It's shabby in comparison to the iPhone 5 version, albeit superficially. Laggy animations with gestures / rotation are my main bugbears.
It's a bit disappointing that it's not delayed, to be honest. Yes, it's perfectly useable, but I cannot agree that the iPad 4 should be receiving a markedly sloppier rendition than iPhone 5. That's not how you'd experience iOS 6 on the same formats.