Killzone is pretty fun. Feels a little more like CoD than PS3 Killzone games. - Agreed
Uncharted ain't bad, but I'm annoyed by use of gestures, touchscreen, etc. - Most of that stuff is optional, I believe. I really liked this Uncharted though. You should give it a chance!
8GB is not enough, those two games basically filled it up. I have numerous other games I want to play eventually. - Definitely agree lol. I've only got an 8GB as well. I need to constantly be deleting and reinstalling stuff.
The device is uncomfortable for fighting games and other games I would use the d-pad on. - It's not the best D-pad but it's better than most other handhelds for that.
PS Now works great, can add great value to the hardware, but the library kinda sucks. - PS Now is not even available in my country so there's that 
Some recommendations:
Dragon's Crown, Persona 4 Golden, Danganronpa 1-2, Guacamelee!, LBP PS Vita (really good!), Tearaway, Velocity Ultra and 2X, Tales from Space: Mutant Blob Attacks, TxK, Zero Escape: Virtue's Last Reward, Lumines, Gravity Rush, Super Stardust Delta, Ys: Memories of Celceta, Soul Sacrifice Delta, Disgaea 4, Wipeout 2048, Muramasa Rebirth
