Only one I'm really interested in is OlliOlli 2, will play it on the train in tomorrow. I will probably try Valiant Hearts eventually, since I heard it was amazing.
Also, Helldivers just came out today on PSN for all platforms and I can't recommend it enough. I'm playing it on Vita and it's every bit as good as the reviews say it is.
OlliOlli (edit: Counter Spy as well) is cross-buy, so you can download it for PS4 as well. That's really the best part about PS+: it's 6 unique games, 2 per platform, but at least 1 or 2 break out across multiple systems, with Vita typically making out the best. There have been a few months where we've gotten 4-5 Vita games, good trout, too, like Spelunky, Binding of Isaac, Proteus etc.