^^ Oops, yes but still this is an expensive battery holder...
^ If you look at the iFixit the electronics (CPU wireless etc) is along one side, would not pre surprised if there is what the heat is coming from. The display might have improved, but I do not think the other components really have. This display should have been on the iPad2, then that would have been a good improved model.
Oh, and who makes the display? Samsung! Seems they are the only one who could produce enough numbers and quality.