I've tried most media players (Songbird, DoubleTwist, Winamp, etc.) but I like iTunes the best. I have to use it anyway, because I have an iPod Touch. I know I can sync it with other media players, but it would only sync music and video, and not apps, podcasts, etc. I also listen to a bunch of podcasts, and iTunes is the best for that.

I do use VLC to watch videos, however. iTunes video playback has always been really slow for me. It's mostly because my computer is shit, but VLC works fine.

I do most of my music listening with the Last.fm application anyway. :p