Just by way of experience - I use an Apple Powerbook G4 with a 17" screen. I've used it from DFW to/from LGW on AA 777's, and DFW to CDG on AA 767's. The computer charged itself and we watched movies. No problems.

The 777 seems to have power in every row. The 767 does not - you have to work out a seat that has it.

I've also used the same machine on AA 737's and on AA MD-80's.

It works better if the people sitting ahead of us either both sit up, or both recline. If one sits up and one reclines, we have to watch at an angle.

And I discovered on our most recent trip that the PB fits nicely in the external pocket of my rollaboard, which means I don't have to carry it. Nice!