It's very very slow, it crashes often, the UI is weird and hard to figure out (maybe it's more intuitive for Mac users?) and it has several annoying bugs: when syncing with my iPod it often marks podcasts I've listened to, or partially listened to as unlistened; it often hangs when trying to connect to the iTunes store (this is remedied by running "ipconfig /flushdns" at the command line); if I buy something from my wishlist it only removes from the wishlist about half the time. And every time it updates itself it tries to install Safari...