Game is pretty cool. Story mode is entertaining, I'd say about 10h. Finished it in 2 days. Storyline is interesting(MK-wise).
AI's a bit annoying, their method of a sure-win involves using the same move over and over again, especially with Shao Kahn.
Which leads me to my point - if you have a choice, don't buy the game for the Xbox360.
The Xbox360 controller just wasn't made for Fighting Games, and it'll wreck your analogs pretty easily. I've had my slim-controller for a couple of months now and it's always worked nicely. 3 days with MK and the left analog is constantly tilting to the right, ruinning most combos in-game. And I'm not that much of a 'rager'. But the really annoying thing is the d-pad. It's badly built for fighting games and many times you'll find your combo broken by the diagonal keys in the d-pad as you move your thumb across positions.
If you don't believe me just check the other reviews online for the Xbox360 Controller, same thing happened with Street Fighter, which prompted them to release a special controller(for hardcore gamers, but still). Also, I'm not sure this game is worth buying a special controller just for playing it(like one of those £20 madcatz ones).
Still overall it's a fun game to play with friends. But really, if you can, buy it for the PS3.