A really good FPS who has similarities to Half-Life games + interesting guns + timeshifting abilities.
The other thing is of course the time factor. You control the time and it's so much fun. You can stop, reverse or slow-down time. Personally I mostly used stop or slow-down time effects even though you can use any effect almost anytime in the game. They are easy to use and helpful. There are several puzzles where you must use your timeshifting abilities to solve them. The game also has some vehicles you can drive but they won't become the main concept of the game.
Probably, the biggest negative for this game is the story. You get all these weird 'missions' from your friends that you must accomplish even though sometimes you don't even understand why you are doing it. Also, the ending is horrible. It's simple and fast. I was expecting something more dramatic (i.e. final battle). Also, one more thing that is really annoying, is whenever you start a new segment of the game (new chapter) there is a Loading screen + Processing Shadows screen that also takes place at the same time which makes loading twice as long and twice as boring.
I really believe that the game was too under-rated by GameSpot and that it deserves a much higher score..something like the one below:
8.5/10