I picked this gadget up in the groupbuy on the EE a couple weeks ago.  I finally got a chance to take it out.  

The claim is that it reduces recoil and allows for faster followup shots.  I have to say that it performs exactly as advertised.  Of course,  an AR doesn't have much recoil, but with this buffer follow up shots stay right on target.  My AR feels like a .22 LR now.  It just makes shooting it more fun.

I'm running it in a RRA midlength with a magpul stock.  

So far, so good.  For comparison, when I went from the standard carbine buffer to the 9mm buffer, I really couldn't tell any difference. Going from 9mm to the MGI, I notice a huge difference.

thanks for the report!

Damn, I missed that group buy by 6 hours, and I am still pissed.