One of the best things about 2K China's port of Firaxis' tactical squad-based shooter is that this iOS (iPad and iPhone) version is the exact same full game as the PC and console releases.
Sure, the graphics have understandably been dialled back and some of the unnecessary animations removed, but
it's the same expansive adventure packaged into a 1.8GB download from the App Store.
XCOM goes against the grain of the portable gaming ethos in that you can spend a lot of time playing it. It's not strictly a game you can pick up and put down for a few minutes at a time. Because of the nature of the turn-based combat, including the turns of the alien invaders, levels and missions can take a while, and that's not counting the resource and facilities management back at XCOM home base.
I've never been a huge fan of turn-based combat - I find it too frustrating watching the enemy attack me while I stand there and take it. All I want to do is block an attack or dive-roll to cover. But the great story and very competent touch controls had me hooked on the iPad.
Perhaps the only complaint is the inability to skip some of the cut-scenes, especially if you've already played the game on another format.