Mike,
What kind of MP3 player do you have? Or, are you looking to get one.
I have, and love, my iPod. Have wanted one for years and my wife surprised me with the 40GB this past Christmas. As a musician this is the greatest thing in the world. Gone are the days of taking a CD player and a whole case of CDs to a rehearsal/gig. Drop the pod in your pocket and it's done! I use it in the car with and FM adapter and at work.
iTunes can be somewhat clunky at first, but, I think it's much better than the windows media player. Plus, with the on-line store with the search functionality and ease of downloading it's a great system. Another cool function of iTunes is the ability to share your library with multiple computers in your home network. I have my main "media" PC in my studio setup as the "master" sharing the library. iTunes is loaded on all our PC's. We can now get to ALL of our albums from one central location. I have a small laptop that I paid $100 for, upgraded the memory to use XP and now have this hooked into the main stereo in the home theater. No more loading CDs!
One caveat to iTunes though. It only runs on XP. So, depending upon your PC, you may have to upgrade to XP (about $79) and add additional memory so that XP can run (about another $50 to $100 depending upon how much you need). Also, iTunes is a memory hog as well so take that into consideration as well if you have to buy memory. You probably want to have at least, bare minimum, 256 MB total system memory.
Hope this helps.