Well, I got sold their Korean FAL mags, passed off as Austrian. They were in wrap, and I bought several from a table that had both new and used Austrians as well as some IMI and others. I had no reason to doubt the guy and the finish looked different, but other than that they were very similar.
When I got home, I found that they wouldn't fit. Too big. I took 'em back, guy jams 'em in his rifle and says "see?" I got my money back and saw him selling 'em nearly a year later as the same thing, telling another guy "see?". Now I know he sells counterfeit so I don't deal with him.
But I've heard others say they work. If they would have fit, I'd think they would be okay actually. They are very similar. I hear the Glock mags are junk.
If you get EUROPEAN AK mags, I can't see how they'd be any different than any of the other steel AK mags. I've used 'em in the past, mostly German, and had no problems at all. The bakelite Euro AK74 mags were some of the smoothest mags I've ever seen period.