I played the same song with Winamp 2.91 and iTunes 4.1.1 under Windows 2000 SP4. The results are a bit... frightening.

Thing	Winamp	iTunes
Memory	4MB	30MB
%Proc	<1%	>7%
Behaviour under normal computer use	no effect	playing skips

Well, with iTunes you're back 8 years ago, when you could practically do one thing at a time with a PC.