I have a Blackhawk Serpa for my sig too. But, a Serpa retention holster is the kind that you must be careful with. There is a history of people shooting their foot. You have to press the release with your finger and if you keep pressing after the pistol has cleared the holster (easy to do) your finger will go right into the trigger guard. From there it's easy to accidentally pull the trigger and shot off your big toe.
Hmmm. I can see how that might be an issue for some. Constant practice of the draw puts my finger along the length of the slide, not inside the trigger guard.