My personal experience with AGP has been great. I bought two AGP magazines earlier this year off the saiga-12 store. I took one out to the range on Saturday and I heard a click while loading ammo into it. I disassembled the magazine and the spring fell out in pieces. I contacted AGP via email and Kevin got back to me on Monday and offered to ship me two replacement springs, explaining that there was a batch of springs that were incorrectly heat treated.
I'd recommend AGP for their great customer service.