This french guy is a respected gamer/blogger and he was not convinced by Uncharted: http://gamingsince198x.fr/entre-nous/playstation-vita-la-portable-ultime/
He says it is the best looking game on a handheld, but then complains about framerate issues which spoil the experience. About Modnation Racer, he says it's a joke with huge framerate issues, huge loading times, while the game is slow and bad looking. About the hardware he says the screen is not the wowser psp was at the time, and analog sticks feel fragile.
Dunno how he wasn't impressed with the screen, it's leagues ahead of PSP. Blacks look grey on the PSP in comparison.