I've got the polymer Grippod. The major issue with them is that if you like your VFG near the magwell, it makes for a poor bipod since it works better as a bipod when it is run out towards the muzzle. If you like your grip out there toward the front, then it isn't a bad compromise.
As grips go, it is a nice grip. It attaches solidly. You don't need to remove other gear to take it on and off the rail. It is well constructed and comfortable to use.
As bipods go, it is so-so. Because the bipod legs are shorter than an actual bipod you don't get the same degree of stability. Also the bipod pops out whereever the grip is located (as mentioned earlier) and often is not in the ideal bipod location. This can be seen as either a plus or a minus; but the polymer is also "twisty" enough to let you track side to side to some degree as well with the bipod deployed.
It is definitely a compromise item; but not a bad one. You would have a hard time getting both a grip and bipod that could fill the same role and not take up more than 7oz weight. Right now I am using it on a project rifle that is designed to handle fast shooting close-in and still be able to do MOA shots at 600yds. Unfortunately, I've had issues with other parts of the rifle (that's why they call it bleeding edge technology I guess) and haven't got to use it as much as I would like.