I've played the God of War HD collection (those psp games), Ico/Shadow and Tokyo Jungle via Remote Play and I've been mostly pleased. I'm generally sitting 5-10 feet from my PS3 when I'm doing it though (remember, your Vita makes an adhoc connection to your PS3 for Remote Play, doesn't go through your wifi router).
The biggest problem for me is rubber banding when platforming when a lot is going on - never an issue in Tokyo Jungle but a lot of crappy deaths in GoW because the stream suddenly 'rewinds' mid jump. I agree with StryderOmega though - it's always felt like the PS3 + PSP/Vita were a beta test for the concept. Since it's mandatory for PS4 games I would hope they would make it slightly less sucky.