I've had one for a few months now and I don't actually use it very much. During a game, nobody can understand me if I try to talk. Forget using a radio. I don't know if a throat mic and headphones would make it any better.
It IS very flexible, and you can put your cheek right up against your stock. It makes breathing a tad harder and louder, but not too much so. Water seems to like to condense on the mask more than my goggles, so the inside of the mask will be wet before the goggles start to fog. Not sure if that's a pro or a con. It does keep your face a bit warmer, which is usually a con and leads to fogging.
If you wear it with a helmet and goggles and you pull it down to talk or eat or whatever, you'll need to take your helmet off to get the thing back on. It IS possible to wear it with a MICH 2000 and FlakJak goggles. Presumably other helmet/goggle combos that work for you. If the goggles fit your face well normally, then they should fit just as well with the mask.
I haven't tried it for an extended period with goggles and no helmet.
Overall, it may be worth it for CQB if you like your teeth. For woods, some other form of mouth protection would be more practical.