I didn't know it had both shoulder buttons - my mistake. I doubt the ergonomics though. I'm also very uncertain about the screen's use in core games. Might be good to have a map/radar always available - often in games I'll switch between, and having one on hand not cluttering up the main display would be good. I can't see the touch interface being much good for the mainstream though. An FPS has all buttons and thumbs in action at once. Time taken looking down and moving one hand over to the screen and back is quite a loss in the midst of a battle. I guess a lot really comes down to how devs use the new options, but in this regard I'm pessimistic given lack on interesting and worthwhile implementations of other new and exciting possibilities like sixaxis and EyeToy.
You have a point as cross-platform developers will likely go for the common experience. They will need to entice the partners to do something special, or at least do it in their first parties to boot.
The Wii U pick up rate is unclear at the moment, but it already adds an extra porting effort for developers.