Come on folks this is getting silly.
I own an ipad 3 and apart from the lag between letters and numbers I have not had any issues. This device is a year old, sure not old by any standards but not brand new either the software is BRAND NEW! Why would we expect no lag? This nonsense about wall papers!?! Seriously how often do you all change wall papers? For me this is about every few months at best! I think its absurd you are all moaning about something so abstract!
Because it's not just simple tiny input lag when you change wallpaper it becomes completely unresponsive for a good 15 or so seconds, I'd expect something like that from a garbage $90 tablet from Walgreens not from the iPad 3 and especially not from the still beastly iPad 4. Apple has been marketing the hell out of the parallax and dynamic wallpapers so yeah there is a good chance everyone is going to want to try changing them after they install this update on their iPads and think they just broke something.