I think I'll start posting this here - just to give you guys an idea of what is going on behind the scenes. Also - I'd like to hear everyones opinions on whether I should release daily updates (as I currently do for testers) or aim for more stable release versions? Personally I'm a cutting edge kind of guy, so prefer to get changes out as soon as possible.

2007-09-09
(+) New class BeatmapManager handles loading of all beatmaps initially.
(+) Metadata input dialog accessible using the "song information" menu option, or from the options menu.
(+) New version of song selection menu. Full song access once again
(+) Options menu. Still empty, but its there!
(*) Fixed some misaligned controls.
(*) Lots of new additions to SpriteManager. Handles easing in tweens, hover transformations, more origin and scaling types and quite a bit of other stuff I needed to get the new menu working.
(*) Default button settings on dialog popups.
(*) High score list stores up to 5 scores per song.
(*) Title song is random.
(*) Removed shortcut keys from main menu (and redirected others).
(*) Fixed bug where md5 could not be read of beatmaps in some cases.
(*) Titles with ':' characters were getting cut off.
(*) Holding down shift while increasing/decreasing bpm.
(*) Video sync added to [Events] section of osu files.
(*) Refinement of video texture copy code. Hopefully improved performance on some systems.

2007-09-10
(+) Ranking screen initial version.
(+) Dynamic health calculation. Totally changes the scoring system to be a lot more dependent on combos (similar to ouendan!)
(*) Fixed bug where mouse cursor doesn't retract during transitions.
(*) Converted all scoring types to enums.
(*) Increased the speed of the hitmetre Ki to match ouendan. Also ensure that it reaches max before the first hitObject is hit.
(*) Added delay where click is not accepted after auto-clicking on hover.
(*) Fixed bug where equal scores would be recorded more times than should be possible.

2007-09-11
(+) Basic options.
(+) New song setup dialog with difficulty settings.
(+) Support for named high scores.
(+) Some basic audio samples in the menus. Spinner bonus sound sample. Fail sample. Weeeeeee.
(+) Bonus shows on spinners.
(*) Editor titlebar displays current filename.
(*) Updated selection screen to show rankings.
(*) Added support for multiple beatmaps per song.
(*) Improvements to interface in lots of areas.
(*) Removed video rendering from editor (video can't skip around yet - need to implement this).
(*) Added a confirmation dialog when clearing all beats from a song.

2007-09-12
(+) Difficulty stars next to song in selection mode.
(+) Most of difficulty settings now take effect! This includes beat size, hp drain rate and spinner difficulty. Still a few more minor tweaks to go.
(*) Fix for slider tick rates which are non-integer.
(*) Adjusted menu somewhat. Fixed up the underlying code to support many sprites per song selection box.
(*) Slider lines on timeline were 1 pixel too big. Yes I'm picky .
(*) Limited open/save dialogs to .osu file extension.
(*) Fixed bug where songs that did not yet have an osu were not showing up in edit list.
(*) Set default edit modes on editing a new song - popup song setup window then go straight to timing. Woo.
(*) Fixed bug where screen sometimes does not fade in fully.

2007-09-13
(+) Video seeking, pausing, rate changing. Can now be displayed in the editor . Not on the timeline yet, but hopefully before the first public release this will be complete.
(*) Vast improvements to video synchronisation.
(*) Video texture swapped to managed so changing resolutions wouldn't break. Hopefully not too much performance loss because of this.
(*) Gamefield resizing is back in (ala design mode)
(*) Difficulty wireup for hit accuracy, miss score loss, preempt of circles.
(*) After further discussion, once again changed the hp calculation algorithm. Now ensures a minimum "average HP recovery" per beat in the song.
(*) Slider radius updates after circle size change.
(*) Spacebar plays/pauses the song in edit mode.
(*) Ranking progresses to name entry automatically if left alone.
(*) Graph finishes graphing properly if interrupted with a click early.

2007-09-14
(+) Play/pause/stop controls in editor. About time haha.
(+) Slider points can be removed (right click).
(+) Sliders can be extended to add/remove repeats by resizing the end of them on the timeline.
(+) Grid/time snapping can be temporarily disabled by holding shift. This works for placement and editing.
(*) Fixed bug with gamefield alignment at higher resolutions. Surprised I was the first to notice this!
(*) Fixed spinner placement - behaves more like slider placement with the setting of duration. Doesn't play sounds unnecessarily.
(*) Fixed bug where slider sliding sound would not play on some PCs.
(*) Removed a few redundant menu items.
(*) The osu! logo on main menu now beats in time to timed songs.
(*) TimingPoints are now handled on a higher level (seems like a better place to deal with these too).

2007-09-15
(+) Added version suffix to metadata for songs.
(+) Added a few graphics options.
(*) Same song continues through multiple menus without interruption if possible.
(*) High score entry screen shows what place you ranked.
(*) Slightly more friendly error dialog.
(*) Fixed audio samples a bit more (maximum concurrent samples lowered to more sane limits).
(*) Sliders can be placed with no beat snapping.
(*) Spinner placement icon is smaller.
(*) MPEG and other slow-seeking formats will now behave a lot better.
(*) Added number to fadeout animation for hitcircles. Made them scale a bit further too.
(*) Selection is ordered by difficulty stars if the other fields match.
(*) Fixed video size bug.
(*) Handling no beatmaps present and beatmaps with no notes.

2007-09-16
(+) HAJIMATTAZO! PUBLIC BETA RELEASE!
(+) Osz packaging support.
(*) Fixed md5 checksumming of utf8 containing files.
(*) Slider start circles are closer than the ball.
(*) Score multiple increases with difficulty.
(*) Tweaks before public release.
(*) Fixed bug with osz where it would try to zip itself.
(*) Mousewheel zooms on timeline.
(*) Metronome sound aligned for first beat.
(*) Reduced brightness of screen flashes on selection.
(*) Audio flow is better between same songs different versions.

2007-09-17
(+) Song grouping. How does this work for you guys?
(*) Changed some difficulty settings. HP drain should be a bit more reasonable, i hope!
(*) Extracts .zip files in songs directory as well as .osz. IE doesn't play nicely with archives.
(*) Handle crash when incomplete osz files are still downloading when osu! is started.
(*) Spinner has a bit more acceleration.
(*) Fixed bug where spinner/slider sounds gets stuck playing.

sorry guys - going to have to ignore the results of that poll above for a while. too many bugfixes and feature requests that I am keeping up daily public builds. hope you dont mind ^^

2007-09-18
(*) Fixed some songs not remaining transparent after being selected.
(*) Fixed bug where config file is not saved when using the 'X' button to close the window.
(*) Disabled hitcircle snapping to other hitcircles.
(*) Fixed bug where slider point editing was playing up when a slider was selected, but you hovered over another slider.
(*) Fixed bug where slider end circles occasionally appeared way too large in the editor.
(*) Standardisation of osz extracted directory names and osu filenames.

Keeping up a consistent pace with new features and bug fixes. Surprisingly, there haven't been as many bug reports as I expected. Not sure if people are staying quiet, or the testing process really did filter out the majority of bugginess. Spent most of my time tonight on the filename structure for osu/osz saving and extracting. Everything is really solid now in that regard - and filenames will be assigned automatically based on the provided metadata.

Also started on the video tutorial - did a test-run, but didn't have enough time left for the final take . Tomorrow!

2007-09-19
(+) Basics to allow osu! to check for new updates when it is run, and present an option for the user to get updates.
(+) Linear curve type. Can now place hard cornered sliders.
(*) Md5 can be checked in the currently open application. Changed updater to use this rather than hard-coded version number.
(*) Fixed issue where slider length is saved as non-integer, but causes crash on load.
(*) Fixed bug where resizing a spinner caused the game to crash.
(*) Snapping turned back on for hitcircles and sliders - and extended so circles snap to the end and the start of sliders.
(*) Broke sliders, but fixed them again..

forgot to post last night, whoops.

2007-09-20
(*) Reordered slider-tick sprites to be beneath repeat/end circles.
(*) Two crosses appear when missing a slider altogether, at the start and end points.
(*) No cross appears when missing the start point of a slider.
(*) Fixed bug where short sliders could not be placed correctly.
(*) Fixed bug where end circles acted as start circles too.
(*) Fixed bug where game would crash on entering play mode while a song was playing which does not have any beatmaps.

Graduated from uni - officially! Because of the ceremony I didn't get so much done, but I finished the voice-over for my first editor tutorial, and am encoding overnight

2007-09-21
(+) Circles shake when out of order.
(+) Slider velocity adjustment added to editor.
(*) Hopefully fixed bug with unsupported characters.
(*) Oops, I did a build too early. Removed slider velocity from public version.
(*) Notes under the end of sliders now stack. Makes it a lot easier to see these.
(*) Metronome ticks and metre are a lot more sane.

I'm not sure if I'll have time this weekend to pick up one of the large new features I want to add. Next on the agenda is most likely getting a website together, along with online ranking linked into the game. Might be able to have that done by Monday but no promises .

Been working on a lot of small bug fixes/features which have hopefully made things a lot more solid since the initial public release.

2007-09-22
(+) Login handling.
(*) Update notification disappears while playing/editing.
(*) Increased difficulty of combo end-scores, but introduced a hp bonus even when you miss both types of combo.

2007-09-23
(+) Volume controls in options.
(+) Replay support?
(*) Moved song extraction to selection menu rather than as the game starts.
(*) Game will start even without any beatmaps present. The message will now appear when you try to play or edit.
(*) Menu effects don't play and song selection doesn't change while osu! doesn't have focus.
(*) If fire fails to render, it is automatically disabled rather than crashing the game.
(*) Fixed bug where high BPMs would cause an error when attempting to manually set the bpm via the dialog.
(*) Started on new slider rendering code.

Made some good progress over the weekend, albeit a bit slower than I hoped for. Next public version will probably be a few more days, depending on how things go. I'd really like to get the sliders going with this new code, which will take quite a bit of time.

2007-09-24
(+) Framework for play mods.
(+) Two initial mods - "nofail" and "easymode".
(+) Heavier gridlines to show the centre of gamefield in editor.
(*) Grid resizing/non-standard resolutions handled a lot better.
(*) Fixed bug where editor menu selections would become out of sync after exiting/entering.
(*) Fixed bug with horizontal and vertical flipping losing notes.
(*) Fixed bug where short sliders would not play the end-circle sound in edit mode at higher BPMs.
(*) Fixed bug where songs containing characters which are invalid in filenames were being incorrectly handled.
(*) Fullscreen mode will exit whilst in the editor, and resume on exiting. The editor doesn't support fullscreen at this point in time.
(*) Song continues to play while at the ranking screen.
(*) Added a note to inform about the lack of online ranking functionality for the moment.
(*) Fire starts at 30 combo rather than 40.
(*) Fixed bug where game would not start if fullscreen was set in configuration file.
(*) Made selection of last songs in song selection menu a lot easier.

New version is up! This combines all the changes from the last few days in one major bug fixing and minor new feature effort! A few things have been excluded from this public build - like replay data and new slider drawing code. These will come later this week as they are not yet fully complete and tested.

Enjoy

Edit: Minor public build up after the initial version. Fixed a problem will fullscreen mode.

2007-09-25 (b72)
(+) Added audio offset to options.
(*) Changes to allow other localisations to handle numbers correctly.
(*) Fixed bug where snapping would not work when a song had exactly two timing points.
(*) Changed song selection quite a lot. <b>Need feedback on this.</b>
(*) Fixed sort order when stars are the same but difficulty differs (by a decimal place).
(*) Aaaaaahhh! Fixed spinners being HARDER on easy mode.

Spent quite a while experimenting with new stuff which didn't work out to much in the end. Not as much productivity as I hoped for. Tired too .

Edit: But I fixed two, or maybe even three bugs!

I really wanted to make the song selection centre on the beatmap you have selected if your mouse cursor is outside a certain range, but after implementing this and getting feedback from testers, I removed it before putting up the new public version. I did increase the speed of scrolling through the list while in a smaller area, though. Should help for large lists of songs. If anyone has bright ideas about improvements that could be made to song selection, please voice them!