I've beaten it.
Couldn't have been more disappointed. It's not even a "basic" shooter, it's a craptacular shooter.
I remember reading a while ago where someone said (think it may have been randy pitchford) that it would take 10-12 hours to complete.
BULL****. I beat it in 5 hours and 42 minutes. Hardest difficulty (come get some at the start, couldn't be bothered to play it again if there was one offered at the end).
The ending... Was an absolute insult to the 12 years they've developed this game for. I don't understand how they can possibly justify beating a game that took this long to develop in that much of time and have such a lackluster ending. Not to mention it performs like ****, and the graphics are absolutely ugly. (Not the fact that it's an outdated engine, but the fact that everything looks like it's been WRAPPED IN PLASTIC). Also, the gameplay isn't that great. You frequently bump into random objects, and the controls are somewhat sloppy. The framerate randomly drops and then spurts back up. I've yet to experience a crash, but apparently they're happening. Also, I don't know what people are talking about with this whole "Enemies can kill you in one hit" thing, but it's not totally true. You can take a couple hits, but even then, you can literally kill any enemy in the entire game except bosses with one up close shot from the shotgun.
I'd post what happens but the spoiler tags dont work. Suffice to say the ending is ****ING ****.