Oddly enough, I was curious about the AFG2 after reading the article on Canadian Black Rifle Magazine's website, so I ordered one. Finally tried it out today. Previously I was using a CAA vertical grip. I was skeptical going in about the AFG2 but the science seemed sound, so I decided it was worth shelling out the money to try one, since I didn't know anyone that owned one that I could borrow.
The AFG2 was more comfortable in general, and my hand and wrist did not get as tried/strained during sustained firing. I did about fifty double taps and it worked well for me. I was definitely faster getting back on target for my follow up shot (muzzle didn't climb as much) than I was with the vertical grip. I didn't push it to see how long I could go before my hand/wrist got tired but I know when I was using the vertical grip I would start feeling it before I got to the end of ten rounds.
I encourage you to try one out and see what you think for yourself, but in my case it worked out really well and I can't see myself going back to the vertical grip now.