Okay people, let's be honest.
Windows Media Player:
Slow, Jumpy Sound, Irritating Ticking, Blippy Visualisation, Doesn't have that really cool desktop overlay feature that WinAmp has, and can't even exit at a decent speed.
Oh, Winamp 3 does have plugin support, it's just changed a bit and requires new plugins.
Media Player 9? Must be a Beta. If it is, it PROBABLY sucks crap.
Linux All The Way - I think Winamp might have been before XMMS though.
Just so you don't think I'm being biased, I hate QuickTime as well (what the hell does it need, a bloody Pentium 3 1.5 GHz?)