Funny you should ask. I just picked mine up from Kurt last week. Took the ride out to Bushnell, toured the facility, the whole 9 yards. Kurt was a pleasure to meet and deal with.
End of the week I got out to the range to zero my new AR with the A2 Tak brake.
Accuracy seemed unaffected. I have a TA31 on the gun and my best group was 7/8 inch.
I didn't think the gun was that loud. Guy next to me was shooting a 7mm, bare muzzle and it was loud.
I didn't see any muzzle flash but the range officer behind me commented on it.
There was about no muzzle flip. A little recoil as I had a collapsable stock on it. I since switched back to an A2 and I will try it out again soon.
All in all, not much downside and the muzzle flip was reduced somewhat. Also, the gun just looks better with the brake on the muzzle.