The aiming for UGA is pretty bad. It's clunky and not smooth. I can't exactly explain why it's bad, but it just is. And it's not the Vita's fault it's bad. Unit 13's aiming mechanics are much better.
Is it a curse for recent Uncharted games to have bad aiming mechanics for the single player? At least it was fixed in Uncharted 3... Hopefully it's fixed in this game too.
I agree with this all the way. I'd like to see someone beat it on Crushing without aim assist.