Unfortunately, Apple's release notes for 10.2.1 are the same as they were for 10.2, and give no indication of what's changed. iTunes 10.2 added sync support for devices running iOS 4.3 and brought Home Sharing to iPhones, iPads, and iPod touches running iOS 4.3. is supposed to be released on Friday alongside the iPad 2.
Oddly, the , so it appears the only place to get it right now is through Software Update. Also, Apple's wasn't updated at the time this story was posted to reflect the updated version.