I've played the Quantum Theory demo.
It's not bad, but it's not anything spectacular.
It's fairly slow paced for a cover shooter, the voice acting is pretty monotonous and the sensitivity needs to be fixed in the full game. I'm fully aware that you can change it, but before I did, it was so low that it was painful.
If they made a few changes in the full game, I think it would be pretty fun. As I said, it's not bad, but there's nothing about it that holds my attention other than throwing young women at giant guys to kill them.