My Ipad 4 has a warm screen temp but isn't as uniform as my ipad 3,slightly brighter on the left hand side when in portrait,infact this is the first time I've had a really noticeable non uniformity in the screen on an IOS device for quit a while (ipad2,iphone 4 & 4S,ipad 3 all were good)
My experience of IOS device displays has been :-
Iphone 4 cool - 4S warmer - iphone 5 warmer still
Ipad 2 cool - 3 warmer - 4 warmer still