I got to play the Vita at Discover Mills in Atlanta yesterday.
The system itself felt pretty solid. Didn't feel as cheap as a PSP-3000 to me, which is nice. I really wish they went with gorilla glass, instead of plastic, but oh well. The analog nubs felt small, but I think it's something that will be easy to get used to.
Uncharted was fun - it felt like Uncharted. The touch controls were annoying, especially for menu navigation. I really hope this is optional in the main game. Graphics looked on par with UC1, except for the fire effects. Those looked pretty bad, but I'm assuming this will be improved with the retail release.
Sound Shapes was by far my favorite demo - from the previews I'd read, it seemed more like a music creation game, but the demo was straight up platforming. You'd pick up little lights, which would layer more instruments/sound effects onto the music track. Really fun. They had headphones available only for this game, and the sound design really sold me on the game. I'd have no problem paying retail for it, but I really hope Sony doesn't charge $40 for it at launch - I think it'd really hurt the game's chances with the mainstream market, since the graphics are simplistic.
Hot Shots Golf looked and played fantastically. Not much more to it - it'll probably be my most played game on the system for the first year.
Didn't really play much of the other games available - LittleBigPlanet felt like LittleBigPlanet. Same for Modnation. Little Deviants wasn't set up, so I didn't get to try it. Overall, I'm looking forward to the system, if only for Hot Shots and Sound Shapes at launch.