I had a Gen1 MBA. It had terrible overheating problems. Replaced it with a Gen2, with a little help from Apple, and it mostly doesn't overheat. Much better, actually. Once once in a while, while working outside in direct sunlight, have I had an overheating problem with the Gen2.
I would guess that, given all the problems Apple had with overheating and the Gen1 models, that they would have designed it specifically to avoid those issues. Apple doesn't usually repeat the same mistakes.
That's good to hear. I love the form factor of the original and am considering one of the new ones, too. I can handle slightly slower performance for the tasks I do, but overheating gets annoying very fast.