I haven't done a whole lot of testing yet, but the Tapco mag for my Golani worked fine.
I wasn't super impressed with it when I first bought it. Just looked very flimsy and too "plasticky". Full disclosure, I have never used polymer mags before so I may have been experiencing some cognitive dissonance.
The Tapco mags feed just fine. When I was actually loading them they actually felt more solid in the hand then they looked in the bag they came in. It was really weird. If I put on a blindfold and loaded it, aside from feeling like plastic, I wouldn't be able to tell the difference between it and my steel mags. Spring feels firm as you're loading rounds.
I'm interested in seeing how it holds up over time, but magazines really are supposed to be disposable so as long as I can get a few years out of them I should more than get my money's worth.