I'm holding off on the Vita precisely because I felt burned by the PSP.
It's the games, stupid. When the system first emerged, my inital thought was "Damn! Nintendo is sooo unbelievably screwed." But the launch titles were a meager offering, and with several notable exceptions, improved little over time.
My PSP has been sitting in my junk drawer, and I don't have a lot of space left in that drawer for a new device. While Naughty Dog's launch involvement does give me some hope, you can't build a platform around one AAA title...