I'm perfectly happy with my 12" Powerbook. I actually managed over 4 and a half hours of battery life (albeit I was only running a Word Processor). This turned out to be a pain actually, since I was trying to drain the battery to calibrate it.

I don't think the Powerbooks warp. I have noticed a very slight rocking motion depending on which surface I place the Powerbook on (either because of the rubber feet underneath or the unevenness of the surface). This is similar to my dining set where the chairs will either rock or appear perfectly stable depending on where I position them on the floor. A good test might be to find a surface on which the Powerbook does not rock, and place it on this surface periodically to check for warping. I'm confident that people will find that this is not the case.