I have shot harris bipods all my life and was seriously interested when a new, sleeker looking, better mousetrap was supposedly created. I recently got to hold and mess with a harris S, GG&G, and Atlas all side by side and will say the harris and GG&G feel a lot more solidly built. They both had a lot less slack in the whole mechanism. The atlas looks as if it might be quicker to adjust height and panning than the other two, but for long distance shooting the extra slack in the mechanism really worried me.
For what its worth my favorite of the 3 was the GG&G with the tilt and pan feature and flat feet. at $210 (at a gun show) it didn't hurt as much as the $270 for the atlas.
But you know what they say about opinions.