I have and use several Serpa holsters (all I can find local), including one for IDPA. I've had the one for my 1911 the longest, probably going on like 5 or 6 years now, and the only issue I've had was what an above poster noted, I fell on the bastard and slid about 30 feet down a hill with about 50 pounds of gear in a three day assault pack on my back. When I stood up and re-situated/bitched and cursed I noticed that the button was jammed, I had to sit down, take it off and dig out some mud/gunk before I could draw the pistol.
No problem for me that day, a minor annoyance, but I've decided to start looking into another holster like Bladetech because of it. God forbid I was running for my life when that happened I would be dead because of some mud and grit. Not much fear of that sort of thing during an IDPA match but the button does get "tight" some times which puts a slight hitch in my draw that I don't like. Guess I'll have to bite the bullet and order a holster online (I like to feel how they function and carry before I buy).
Also, I've never felt like or been worried about shooting myself while drawing from it. Maybe it was because of my father's constant drilling me about gun safety when I was young but my booger hook stays on the frame on all pistols until the muzzle clears my body, regardless of whether the holster has retention or not, but the button tends to leave my finger in the perfect position on every pistol I have one for to not put my finger directly on the trigger.
I think all mine are level 3 but it's been so long since I've bought them I'm not 100% on that, FWIW.