I have a question about these tablets they're introducing. I found this picture and I assume this is what we're talking about...
That answers part of my question, which was, do you have to hold the tablet for the the duration of the flight. At least it appears that it can clip onto your tray table.
Is there some way to use it with the tray table up? As a fat guy with long legs, I find the tray uncomfortable to have down for the whole flight (especially if the person in front reclines at all). So, it's nice to have the screen mounted in the seat in front of you. It would be nice if the tablets had some way of being attached to the seat in front of you in the same way.