I use it. It works fine in AR's, but it is messy. I like it because it's easy - jam the hose attachment down the chamber, and spray for a second or so. It squirts out the muzzle. It's messy as Hell, with the overspray and just general mess, but it's easy and does get all the surfaces - and is chemically formulated to yank out copper fouling - which is easily visible as blue foam. Let sit for a while, while cleaning the other parts. Push out the blue foam with a cleaning patch on a rod from the breach. The gas tube is stainless, it doesn't mind the foam. I try to avoid getting it on the aluminum receiver, though I haven't seen any evidence that it hurts anything. I like it on pistol barrels, as those are small and simple.
I haven't had any problems from using it.