Quick bug I found, if you change anything on the personal settings page (like the theme) Subsonic "forgets" your last.fm password and will throw a failure in the log stating it couldn't scrobble the track. You then just have to re-enter your password and save it again in personal settings. I guess the fix could be to move last.fm to it's own separate tab in settings or to figure out why it is dropping. Honestly I wish it was on it's own tab because most of the users on my server don't seem to find it very quickly (if at all) in personal settings.
Big fan over here. Subsonic changed the way I listen to my music.
Thanks!