The camera can have a weird feel. Like it is limiting how fast I can l look around. It is a slow limit no matter how high the X sensitivity is (and my mouse DPI is 1600) so naturally when I try to look around it causes me to look vertically as well. If you saw my gameplay it would look like someone who is new to a computer is playing. After awhile, I get used to it and move my mouse as fast at the limit is which fixes the unwanted vertical-look issue I had.