After a full day of messing with it on and off I have to say I'm pretty impressed with what the hardware is capable of, such as the rear touchpad interface, the tilt sensors, etc. But the question becomes will they be able to implement these features into games in a manner that feels natural and not forced or gimmicky.
The first game I've been playing is Rayman Orgins which I guess is a port, and at times, because of screen size, it can be a bit tough to play for my old eyes. I'm eager to play a game that was built from the ground up specifically for the Vita to see how goes. I have Uncharted coming in the mail in a few days.
On a side note, a big FU to Bestbuy.com. I ordered the Vita, a 8 GB memory card, and the Uncharted game all at the same time on the same order, and what does BB do? They ship all 3 separately with different carriers. They made sure I got the Vita on 2/22 but why in the hell they didn't put the rest of the order in the same box so I could have had it all the same time is beyond me.