Is Gravity Rush good? The demo really didnt hammer anything home, but it was probably the best demo I tried.
Runner up would be Escape Plan, but the controls eventually got to me (having to pinch the screen was stupid as fukkkkkkkkkkkkkkkk)
Sound Shapes is pretty neat in that FRESH INDIE way. Reminded me of some flash web game tho.
I didnt try Uncharted cause I gots to play some Uncharted.
All the other demos I tried (I didnt bother with Hot Shots, Lumines, etc. -- I know how these play) were doodoo or gave me wicked PSP flashbacks. As in, "gee, this looks like a PSP game. Ok."
A lot of Vita games really use the controls against you. Even that freebie Montezuma Revenge. It has me rub the back of my screen, while using the frot screen to move gems. How the fuck?