I've had my vita for almost a month now and have got through part of the ps plus backlog so I think I will post a few opinions on the games I've played.
Uncharted - Great game, annoying touch controls at times and the shooting I found a bit tricky but otherwise excellent.
Gravity Rush - Another great game but with annoying controls when you have to deal with larger bosses
Rayman Origins - The best platformer I have played, the levels which lacked music were lowpoints though.
Sine Mora - A fun bullet-hell shooter, but not something to spend hours on.
Tales from space - A great platformer with some really enjoyable levels, almost as good as Rayman
Thomas was Alone - An okay platformer, lacked the atmosphere of Rayman and Tales from space though making it a bit dull.
Lumines - a great way to spend half an hour of your time, great songs too
Jet Set Radio - I did not enjoy this at all, deleted it after 1 hour of gameplay.
Cocunut Dodge - A good game but something I would expect to play on a phone though not a console albeit a handheld one.
Unit 13 - from what I've played it is an enjoyable third person shooter, ideal for gaming while travelling to work
Wipeout 2048 - Another game I didn't enjoy, I tend to find racing a games a bit boring so it's not really a genre for me.
I think I will probably buy some software now, Hotline Miami looks really good as does Killzone. Persona 4 is a game people mention a lot when reading this thread but I played Ni No Kuni so I amn't sure if JRPGs are my thing so might pass on that one for a while.