....sigh, still down.....actually I can't connect to either Bancho (osu.ppy.sh #osu) or the older IRC (irc.ppy.sh #osu). They both give "* Connection failed. Error: Connection refused" lol, i can still watch online replays tho ^^
Bancho goes down from time to time. I think, rather than having people post all the time, there is a thread, or HELL, a PHP script that, like, pings the server on request and tells you if bancho's up or down.
Online rankings and replays and stuff aren't done through bancho (from what I can tell) hence why those work when bancho's pooched.
Just to update you all - there have been a few minor (read major?) problems with bancho with regards to threading. Its been a very difficult problem to track due to the nature of the situation (only happens when many users send many commands at once), but I think I've gotten to the bottom of this through some redesign.
I am hoping it won't, but if bancho does crash again don't panic. You can still submit scores, access rankings and pretty much play the game without interruption and your osu! will automatically connect within minutes of it becoming available (based on exponential back-off - if bancho restarts fast it will take 10s, otherwise up to INFINITY MINUTES!!1).