iTunes is great... on a mac.
The PC version however runs very slow, corrups, crashes, has odd graphical glitches if you have a large music library and is bass ackwards to use. WMP may not be the best media player on earth, but I have never had an issue with it trying to reorganize my library (like itunes does), rename my music that I created (like itunes does), swap out album artwork when I found a better quality pic than they did, and when I click on an artist and press play, is stays on that artist without the need to make annother useless playlist!
And lets not even begin to talk about the fun my wife and I have had trying to get her damn ipod to sync properly with the songs she actually wants to hear. Or the weird permissions issues we have run across where her ipod thinks that the computer that just spent forever loading it with music, is somehow not the proper computer or user information, so it needed to be reformatted again to change 2 songs that she forgot to put on the thing. And God help you if you actually use WMP for day to day use, and use itunes just for the ipod syncing.
Seriously though, it's not all that terrible to use anymore, and they have addressed quite a few issues. But I would still like to see it become a little less intrusive, give a few more options to users, and take care of some of those dumb corruption issues that still crop up from time to time.