Well it seems that games that don't actually need to have a large part of their controls on the pad can do it easily since all the rendering is done on the machine anyway. But how would you take zombie-U to the small screen? Maybe a toggle to go into the inventory I guess.
Shit - I'm sure that was one of their main original selling points when they did the first reveal of WiiU? I thought that was 50% of the reason they went for a Gamepad with a big screen they could stream gameplay to - so that you can play the games on the move. I can imagine only Nintendo games will end up supporting it.
I was more eager to just take my game up to bed with me than I was to having a map screen on my lap.
It's a massive dent if it isn't universal IMO.