A lot of effort was put into this game and it shows. Many small details that make the gameworld more immersive..
Many game engines could learn something from this one. Especially smoke and human models are very well done. There should have been a few more models for humans though, as you'll feel you've seen too many twins by the end of the game :)
The final level was very enjoyable as well. Not your conventional end-game bossfight for once.
If you're looking for an action-packed FPS that is every bit as much a linear rollercoaster ride like CoD4 & 6 then you should definately check this one out. That is, if you can stomach a slightly weak story and the whole mutant setting. :)