I prefer foobar2000 on Windows for a pure, unadulterated, customizable music player, but Songbird is the best player I've found on OS X. It is fast, plays music, and has a plugin for last.fm, which is everything I require.
I've had the opposite experience; while with a fairly small library Songbird is fine, with mine (~700GB, lossless) it's incredibly slow and prone to crashing. Last time I tried it was about six months ago with no improvement.
I prefer foobar2000 on Windows for a pure, unadulterated, customizable music player, but Songbird is the best player I've found on OS X. It is fast, plays music, and has a plugin for last.fm, which is everything I require.