It seems the panic for AR mags is slowly dying down but a mag that's relatively new to the US market (I think I got mine at the end of 2011, maybe early 2012) is availible pretty consistently from a couple websites (Midway, mwgco.com, and others....). Here's what I've found so far...
-Reliable. I've never had a malfunction using these mags.
-Available. They're in stock and ready to ship.
-Designed Ivan Kolev (designed the SLR 106 mags for those that care about that kind of thing)
-Steel reinforced feed lips. Lots of folks prefer this over the all polymer competitors. Me, I don't have a preference either way as both Lancer and PMags have been extremely reliable for me over the years and one uses metal, one doesn't...
-The ribbing gives a good positive grip on the mag when inserting it.
-They weigh 6 oz
-No issues with inserting when fully loaded and they drop free.
-They're not going to fit in a lot of mag pouches.
-They call their follower a "stable, level follower" but I'd rather see an anti-tilt design personally. Again, they've always been reliable but non anti-tilt followers just make me think of old school USGI mags... and not in a good way.
-Cost. They're $25 which may not be too bad these days but deals can still be found on 30 rounders so the cost may be prohibitive for some.
Here's a video review where I do a little shooting, break down the magazine, compare it to a D&H mag (with Magpul follower), and discuss the pros and cons of the mags: