I've had this sitting on the shelf because I didn't really like the demo, but today I've put in a few hours and found it surprisingly fun.
It looks really great, controls well, and the weapons are pretty good. I like how the enemies move especially when they're being shot, and the AI seems on par with every other FPS. Ammo is quite plentiful so I find I use a lot more weapon functions instead of conserving certain ammo.
I'm playing on the hardest and it's a decent challenge, I die now and then. The time stuff is neat but I'm still getting the hang of it - the window isn't very long which is good because otherwise it would be too much of a "win" button.