Originally Posted by drtravel
I have a 15" Toshiba and a 17" HP and have made had to make use of both when in coach, although it was more effort than benefit overall. Batteries barely last an hour on either one. The Toshiba has a detachable wireless keyboard, so I prop the laptop up straight like an easel in the empty adjacent seat and keyboard from my lap or the armrest. Where there's a will, there's a way!
I've used my 17" Apple PowerBook (my only computer) in coach more often than I'd like to be there in the first place. It's a bit over 15" wide, screen measurements are diagonal, so it fits. Not much room left over for other stuff, it helps if there's an empty seat next to you, but definitely possible. (It also helps if you're skinny.) FWIW, I get a lot more battery life than that.
As for a 20" screen, though - it's likely to be 18" wide or so, as wide as the seat, so even aside from height issues vis-a-vis the seat in front an empty seat on one side would be mandatory. I also don't see lugging all that weight around. A 17" screen, 1680 x 1050, lets me see two full pages side by side, or the equivalent in other apps. That's all I need. YMMV.