This has no right to play as well as it does.
It's still not quite as precise as a traditional controller with my movement, but on the other hand (my only other real point of comparison is mh3u on 3DS) controlling the camera is fantastic - adjustable swipes with the right thumb anywhere on screen or a quick tap to center camera. The adaptation they've done with the attack and roll buttons (tap and swipe in a direction for different moves based on your weapon) is really, really smart. And it runs surprisingly well on my 4s.
Now the only real heartbreak I have is the lack of cloud saves.

trying to decide on my iPhone versus the borrowed iPad mini I'm using now for work is killing me.
I think I still prefer MH3U as a game over Unite, but the iOS version is pretty fantastic. I think Unite probably plays better on my Vita but having this always on me is amazingly comforting. Only real downer is that on my 4S I have so little memory free that there's no real multitasking to speak of, so the game seems to reset every single time I switch to another app or get a phone call.