I read this:
«>oh... be prepared: it's not an issue but... 
>these  little beasts become really, really, 
>really hot: don't even think of holding one on 
>your laps. I'm not joking!

Oh, but heat IS an issue. I'm working in 
unairconditioned places most of the time.»

I am not sure of which portable computer you are speaking. Is it really the 
latest MacBook Air? It cannot be, I am sure. I have bought one, which I have 
been using extensively on my numerous travels, I work on my knees a lot, 
and the wonderful thing of this computer is, THAT IT IS NOT HOT. Not even 
lukewarm.
I have an 11-inch computer, with 2 GB internal memory and 128 GB flash 
storage. I have been using it for the last six weeks (I bought it the very first 
day it was on the market). There is no hard disk, so it does not heat up, and 
there is no noise whatsoever. I was hoping the iPad would be my traveling 
companion, but I was disappointed. The iPad is not particularly good for the 
kind of work I do. The small MacBook Air on the other hand is perfect. 
For whoever reads French, I wrote about my experience at 
http://www.cuk.ch/articles/4686.
Cheers.
Anne