Lots and lots of fun.
Although it was a Build engine game it still somehow managed to look good. Today theres a patch available that makes it look much better. And the level design, amazing.
It has some kick ass weapons, some of them very original. What i liked most that they were so powerful and actually fun to shoot. You even got a nuke launcher, how cool is that? Of course, the shooting range of that didn't allow to use it very often, but i remember shooting it to walls just to hear the cool 'three, two, one'.
The monsters were some of the coolest i've seen in shooters and definately the most humorous. Imagine a huge sumo guy that uses his gas as napalm on you from distance haha
I'm really glad i had a chance to play this game back in the day. Not many games have managed to keep me up all night. The fun factor of this game is 10/10, what more can one ask?