I have a lot of his magazines for the Ciener and the DPMS/Colt kits. The Ceiner can be picky with different ammo, and does not like to be dirty at all.
The blackdog magazines though... I will swear by them, best i have used.
I had heard that the Stainless Ciener conversion kit tends to be pickier about being clean.
I think thats about the only gripe I have heard about it.