Not perfect, but more than worth the 1200 points.
I'll say it from the outset. Shadow Complex is the best and most value for money game on the Xbox Live Marketplace. This is not to say that it is the perfect game, it is certainly flawed, but you'll get as much fun, time and replay value out of it as you would any decent full priced disc game.
You play the role of Jason, an ordinary man out on a date with his newly met girlfriend Claire. Your fun filled cave exploration date soon goes awry however, leaving you to deal with hordes of henchmen, contraptions and a hell of a lot of jumping and crawling. While the story itself is solid, there are aspects of how it was delivered that are really satisfying but at the same time disappointing. Disappointing in that there is not nearly enough of it. The chatter you overhear between enemy units is really well delivered, but few and far between. And perhaps my favourite story moment in the whole game, a 5 second flashback which revealed more about Jason's past, was the only one in the whole game. It is alluded to only once after this and then boom, no more flashbacks. This could have been a really great way to explain a bit more behind your characters motivation and skill levels, and also a bit more of the overall story regarding the Restoration.
Lets move on to gameplay.
Shadow Complex may take a bit of adjusting to. The first half hour or so I absolutely HATED the way the game felt, particularly the aiming mechanics. As I got used to the game, the way in which you control is still not perfect, but you should adapt to it pretty easily so that moving Jason around and shooting should feel pretty natural.
The variety of enemies is great, so too the exploration, item discovery and challenge.
If you like video games, and you have an Xbox 360, then get Shadow Complex