I just got an Atlas bipod from Midway and it's very difficult to cant and pan the rifle.  I thought you're supposed to be able to turn the big knob to adjust the tension, but that thing wont turn at all.  Any ideas or did I get a faulty unit?

Get your kung-fu grip going on.

The one I ordered was VERY stiff the first time I turned it, and remains slightly less stiff than the first time, with repeated use. It's never easy.

Mine was very stiff straight out of the package as well. To fix that I loosened the knob as much as possible, mounted it on the rail and rolled and panned the rifle in every direction over and over....basically put it through it's full range of motion repeatedly. After a few minutes I could feel it loosening up. After doing this a handful of times it was loose enough that I had to tighten up the knob to keep it from being too sloppy.

Mount it up and give it a workout...it will loosen up and the movement will become nice and smoooooth.