A lot of fun
First of all the gameplay is a lot of fun. You have a large assortment of gadgets and weapons to use in a variety of ways to accomplish your goals. You can blast your way through run-and-gun style, or you can go slow and have fun sniping out enemies from far away.
The environments are very large, and some of the later outdoor levels are very memorable.
The graphics are some of the best I've seen on the Xbox with almost no loading time in between different levels. The sound is also very well done, and I like that there was no intrusive music getting in the way.
The story was also pretty interesting, not that I understood much of it, but there were several items to unlock that explained more of the background.
The difficulty level was good, and I think i noticed it adjusting to me failing on a few occasions over and over to become easier so I could get past without getting frustrated - this was mostly on the "Rails" section of the game were it was more a shooter arcade type game.
All in all - very highly recommended! It was a little on the short side, but I appreciate they didn't artificially extend the length by having a bunch of stupid boss fights or something like that.