Warning: this post includes high amount of personal preferences. That's what modding basically is... or so I thought?
Overall, you've used streams too much. I'd turn some of things to sliders, but then again, its most likely I don't like streams. I do think I overused streams for intro, but other than that, I disagree.
00:23:295 - adding a note here sounds better and doesn't harm the flow. And if you don't add note, I'd add gap between those two 1/2 notes since 1/2 is long enough for a small jump. Fixed the second way.
02:32:727 (1) - I dunno', perhaps shorten by 1/4 and add a note between two sliders. <3 Wut? Is that just for variety in rhythm patterns? Maybe, I dunno..
02:38:636 - 02:39:318 - too much gap here, I'd try to fill. Isn't it obvious that this is intended?
03:59:090 (3,4,5,6) - try increasing ds, i think its a good place for it! The stream that took this place before is back!
04:05:454 - 04:06:590 - too long gap. Intended ._.
Else than that I think its fine! Good job.
00:05:454 (1) - I'd remove this but I guess its mappers choice. uhh i mixed mapping piano and vocals and now every modder tells me to remove dem notes
00:27:727 (2,3,4,5,6,7) - IMO ds is too high for hard diff considering they are 1/2's. I used 1.0x for non-kiai, 1.3x for those kiai-like parts that I didn't make kiai lest overuse and 1.4x for big kiais. Also, that's certainly not too high ds, just the fact that they are lined up makes them harder. If they made a zigzag pattern with even slightly larger ds they'd be easier.
02:09:545 (3,4,5,6,7,8) - ^ (In fact those are more spaced than the previous) ^
02:37:727 (7,1,2,3,4,1) - I can't say I'm in fond of these placements, perhaps try something like this? <...> It certailny looks better with your skin, with default one the top slider looks weird.
02:57:045 (2,3,4,5,6) - DS. No, really, just look at 03:04:318 (2,3,4,5,6) - the DS is same.
03:50:908 (1,2,3,4,5,6,7,8) - ^ ^
I really hoped you'd mention some of the doubles in this diff...
Looks good, could be definitely be better, but then again, which map on osu! couldn't be?
Good luck! Thanks :3