I've just spend a month or so, between hurricane drills (shutters up; shutters down; repeat every 10 days), playing with both the polymer and aluminum Grippod versions.
Mine arrived just after I read SMGLee's comments, and yup! He was correct about placement: Put it where you'd put a bipod and it's too far forward; place it back in the usual foregrip spot and it's not as stable as a Harris hung on the end of your barrel.
After playing with it a bit, though, I realized Grippods should not be considered replacements for bipods -- instead, IMHO they are an "enhanced" forward grip, that also can function as a fast-deploying emergency bipod when you need it. I wouldn't put one on an SPR or any firearm whose primary function is long-range shooting -- in those cases, stick to a dedicated bipod. Instead, they are great when you unexpectedly need to transition from CQB and get horizontal fast to try a long shot. They are far more supportive for precision shooting than trying to use a standard grip as a hand-braced monopod, and my drill scores showed a dramatic difference.
A single button under your thumb also makes for faster deployment than having to reach way out there for your bipod.
And during practice, they were REALLY, REALLY great for keeping hot barrels and suppressors from contact burning or melting fabric of soft gear, clothes, etc. after shooting a lot of full-auto. Just brace 'em up and let the breeze do its work, instead of looking for an non-flammable surface to lay 'em down.
If you're fine with both a bipod and a forward grip on a CQB firearm, skip the Grippod. I've snagged too many tight corners over the years, though, and I don't want a bipod in those conditions. For that matter, since I trained in the days before forward grips became popular, I'm not a big fan of them, either. Putting a bipod inside helps me justify hanging one out there.
As always, YMMV.
Now if they could just don something about the
price...