My four showed up today.
No shooting review unfortunately, but I did test them a bit with my 106FR and 106UR SBR. They lock into the guns just fine. The rear lug is maybe a hair bigger than Bulgarian and Polish ones, but it does give a good "click" on locking in. After doing it a couple times it wears in a bit. Both lugs are metal reinforced, which is nice. Feed lips are not reinforced, but I'm also not entirely sold on that being a make-or-break issue. Polish Beryl mags are entirely un-reinforced anywhere, and the Beryl is usually held up as the pinnacle of 5.56 AK design.
I put a couple Magpul dummy rounds in them and hand cycled, no issues stripping them from the magazine. These have the newer (for lack of a numerical designation) generation AC-Unity bolt hold open follower, which makes very solid contact with the bolt. No concerns about it chewing the edge off or anything. Holds open when empty, bolt snaps forward when you pull the mag.
AC-Unity has gotten dinged online for very "flexible" magazines that supposedly compress very easily if you squeeze on the sides. They do have a hair of flex to them, but nothing like what I've heard described. I generally try to avoid crushing the sides of my magazines.
I think it's a non-issue.
I generally like the AC-Unity product line so I'm happy with the AK 5.56 flavor and I'll order another 4 when they come back in stock, as well as the 5.56 45-rounders when they hit. I wish someone would start making some small-bore RPKs already! (Help me Obi-wan PSA, you're my only hope!)