Laptops suffer far worse from overheating, the GF's son has a Macbook Pro from 2007 with a GT8600M GPU, this regularly fried itself to over 85ºc and would hang the whole laptop. After the logicboard failed in 2009 (presumably due to the frying) Apple replaced it under warranty (£700 job for free!).
I've had the same book and system crashes due to overheating is definitely not normal. My book ran for days on full throttle without any trouble whatsoever.
The logicboard failure was in fact a failing GPU, but again, that had nothing to do with overheating, rather than poorly soldered GPU on it's PCB. Rapid temperature drops caused the solder joint to break, which eventually broke the GPU and since it is soldered to the logic board, Apple had to replace the whole board.
My 8600 failed on a regular working day, so no GPU intensive work. I closed the lid to take the book with me, opened it five minutes later and it failed.