Its really easy for me to organize and listen to stuff by genre, artist, album, or add date with iTunes, and it's also easy to categorize and find everything I wanna hear, even if I don't remember the exact name of the song/artist I'm looking for (I love that damn search window!). It burns cds very quickly and efficiently as well.
Winamp always ran glitchy on my pc, and didn't seem to have nearly as many (or as intuitive to use) features as iTunes, too.
I don't notice the 40mb it eats up slowing my rig down at all, or iTunes causing windows to shut down slower. Maybe your pcs just suck.