On the Apple's site they say "if you know iTunes you know the mac."
http://www.apple.com/getamac/software.html My theory is that this may be the next phase of Jobs trying to get people to switch to the mac. Let's say somebody has iTunes on their XP machine. They love iTunes. Now, they get a chance to play on the mac and guess what.. they already know how to use it because everything works exactly like iTunes now. The learning curve for the new OS is now even smaller. Now all that person has to do is get used to things not being so overly complicated and viola they are a mac convert with little work!! (now they know iTunes, iPhoto, iWeb, the finder, Safari, and I am sure the list could go on.... all for just using iTunes)