I don't know, I think if done tastefully a painted interior looks a lot nicer than having black seats and dash with cheap looking gray plastics everywhere else.

It bugged the heck out of me until I decided to put in a new black headliner (needed a new one anyway) and use Krylon Fusion black spray paint to do the panels. Krylon Fusion is the paint to use for plastics, if you are going to do it. Those panels are a year old in the pic, though I've had it in my Jeep for 4 years now and no fading. No sanding necessary, but do make sure you clean it up real nice with some acetone or something along that line. And no, its really not that much hotter with an all black interior.

Now if you are going to paint it something like red, green, or any other color of the rainbow I'd have to reconsider...but black, a darker gray, something subtle to match the interior I'd say ok...but to each their own I guess.