Something that has been bugging me for a while is that when I'm playing music from my a large playlist (~500 songs) then the interface becomes really slow. When switching songs, the UI freezes for about 5 seconds on my Galaxy S. It turns out this is caused by the app serializing the current playlist every time you change tracks so it can restart where you left off if the app is closed. The quick fix for this was to move this serializing to a background task so it didn't lock up the UI every time.
Let me know if you try it and experience any issues.
Patch:
http://www.ragtop.org/upload/subsonic/perf-3.0.1.patch
Binary:
http://www.ragtop.org/upload/subsonic/subsonic-3.0.1.apk