I don't know man, there's a lot of haters out there. Some people claim they're unsafe because it causes you to pull the trigger during your draw, but that's a load of crap, improper training is the cause of those negligent discharges. I've heard a couple of stories about guys getting debris caught in the mechanism causing their pistol to be stuck in the holster, but it's never happened to me. I've known plenty of pipe hitters who have used serpas, and I've always preferred them to safariland. but they have managed to get a bad rep from the interwebs.
Agency issued duty gun, if carried off duty, is required to be carried in issued off duty holster, which happens to be a SERPA. Personally I prefer Safariland ALS to the SERPA, but that's just me.
Next duty gun is getting a Safariland ALS as an off duty holster, I think. I really prefer the thumb release to the trigger release, but it is what it is.