I wanted so bad to like this game.
The physics are great, and the graphics somewhat impressive at times, particularly in the alien ship toward the end. But, much of the game is plauged by cheap deaths that force you to start again from their 'checkpoint' which is in some cases, 5 full minutes of playing backward. Needless to say, this becomes irritating.
There are some laugh-out-loud moments, such as the staged moon-landing tv theater, and other such clever "government conspiracy secrets" that you find on the floor, usually in the form of documents to scan with your handy-dandy wrist scanner.
The weapons could have been more varied. There is the standard pistol, machine gun, shotgun, etc. You are able to get two alien weapons, however, which add to the fun. Somewhat more original yet cheesy is the ability to turn into a rageful zombie like character and swipe at enemies while stealing their life with your "parasite launcher." This form makes boss encounters almost too easy.
Toward the end of the game, I found myself simply playing it to finish it, not necessarily because I was enjoying it. See if you can pick it up cheap.