If you have PlayStation Plus, you can get a decent amount of free games. A free game should be removed today and a new one added, but I'm not sure which.
I do own a vita, but honestly, I don't use it that much. Albeit, I don't use my PSP or DS Lite that much either. It's not a bad console. I do think the OS could be a bit better as it has some wonky aspects to it, but it works.
EDIT:
I took a peek at Sony's online store, and at the moment, the following Vita-playable games are free for PS Plus members:
Tekken 6 (PSP)
Plants vs. Zombies
Mega Man: Maverick Hunter X (PSP)
WipeOut 2048
Uncharted: Golden Abyss
Gravity Rush