I keep reading that guys buy Promags, get upset with them, and throw them away.
I've had bad Promags, and I'm not a big Promag fan, but I've also had good ones. I also know that if you contact Promag with a bad mag, they'll bend over backwards to get you one that works right. Its a little extra expense to send them the bad mag, but not as expensive as trashing several recently-purchased ones.
I've had good luck with Promags for a S&W 69, Beretta 92, S&W 669, a SIG 220, and continuing success with their mags for the CZ 75 Compact. (Don't care for their mags for the standard size CZ, however.) Ive heard horror stories about their mags for the FEG line of guns.