Year bump because I just finished this game.
Game's awesome, recommended to all current Vita owners (because there's really no other game for Vita at the moment).
As far as buying a Vita for it, I'll be honest, debatable.
The use of gravity in the game is interesting, both gameplay and story-wise.
Overall combat mechanics are simple, you aim for cores of enemies and break it with whatever method is convenient, ranging from normal kicks, gravity kicks (with lock-on, like gravitational pulls!), stasis field (throw things, objects do not orbit Kat, unfortunately), or specials like mini black hole. There's a variety of enemies where some methods are better than others, so you probably won't be just kicking everything to death.
Overall gameplay is good. You can get gems to level up your skills (health to specials and all in between), which are found around town. However, you'll most likely use those gems to upgrade the town (very minor cosmetically) which unlock challenges. Challenges give about a hefty amount of gems if you get gold, they range from races to kill count, usually with different conditions all around town. They aren't too difficult, but still fun.
Story is nice. A lot of the devices revolves heavily around gravity and a bit of theory of relativity, you can really see where they play a role.
It's of a decent length (21 chapters). In addition to the story, you also have the challenges as previously mentioned, so this game is actually a good amount of time for a portable game.
Can't wait for DLC, yay!
Also a great title for trophy collectors. Very easy to platinum.