This truly is a great shooter
There are plenty of levels to keep you going for a while, and the good part is, the difficulty adjusts to your skill level. So if you are really going bad, then the difficulty level will drop, but if you are dropping enemies left, right and centre, then the game will raise the ante a bit.
The graphics are really good, but I did notice at some parts that the frame-rate would really crud up.
All in all, this is one hell of a game and you should at least hire it out.