I finally received my first can, and am doing a quick review. This is my first can, and I don't have a whole lot of experience with them so sorry I will not be doing much in the way of comparisons. The only other can I've shot a fair amount was a friend's M4-2000 mounted on my AAC muzzled device from about a year ago.
First and foremost, it easily satisfies it's primary purpose: To make the rifle look cooler.
The suppressor itself is quieter than expected. From hearing many people talk about how loud surefire suppressors are, you would expect it to sound like a .50 BMG going off. I compared it to a .22LR shooting supersonics and subsonic ammo. From 10 feet away, it was easily quieter than the .22LR shooting supersonic ammo (federal automatch). It was slightly louder than subsonic .22LR rounds (tenex). Most of the sound seemed to come from the crack of the bullet as opposed to the muzzle. I last shot the AAC suppressor a year ago, so I can't compare the difference in sound levels. I do remember the M4-2000 sounding different though (maybe a little better than the surefire).
The backpressure is surprisingly light. I remember with the AAC, I got a bit oil on my face and eye protection however there was none with the surefire. The spent brass I've seen come off most suppressed rifles were absolutely filthy and almost black. Brass coming from the surefire was surprisingly clean:
Brass in the middle is unsuppressed, top and bottom are with the surefire suppressor.
POI shift is about .5 MOA, maybe a little less with a SPR contour 18" barrel. With a KAC lightweight 16" barrel, I was just under an MOA shift. Perfectly repeatable on both rifle.
All in all, I've very happy with it.