my iPad 4 got REALLY hot when just web browsing (hotter than the iPad 3 i used to have), wifi sync wasn't working, and it just seemed sluggish overall. i knew something was odd.
i wiped the device clean and restored it again. all problems were solved. however i still didn't see the extra speed i was hoping for and decided to return it and get an iPad 3 64GB LTE-Verizon refurb for $679 instead
i think iOS 6 is to blame regarding speed performance - i find it to be a very clunky iOS version overall. my opinion is based on ownership of an iPad 2 and iPad 3 both running iOS 5.1.1 , and then also owning an iPad Mini and iPad 4 running iOS 6. the iPad 2 with the A5 1st gen runs better than my iPad Mini did with A5 2nd gen. the only difference between the iPad 2 and iPad Mini really is the iOS version. i'm convinced iOS 6 is to blame.
you're probably wondering why i own so many iPads. i gave the iPad 2 to my brother. i bought an iPad 3 only to have the iPad 4 be announced 3 weeks later. apple allowed me to return it and pre-order the iPad 4. i got the iPad 4 and i wasn't satisfied (see above) so i returned it for an iPad Mini. the iPad Mini is great but there is light bleed all over the place and i can't justify spending $659 without Retina. so i returned it and got an iPad 3 64GB LTE refurb instead for $20 more ($679). that seems to be the best value and i'm glad i am back to the jailbreak with BTC Mouse app that allows me to turn my iPad into a fully functional laptop replacement.