I LOVE IDPA. I went so far as to become a certified Range Officer with them. Sooooooooo regret ever paying for a life membership with USPSA. I never shoot IPSC anymore.
My club
http://www.tssa.net has a lot of folks who are DHS and police and even some air marshalls. Some local SWAT types, too.Even a criminal circuit judge! So there is a lot of experience floating around the firing line and we are always learning from each other. That's one reason I went from 1911 to Glock to Sig. I love that IDPA is revolver neutral and there are multiple levels based on classifier rank (so Masters and Experts are never shooting for score against novice and marksman level). There is never a string that goes for more than 18 rounds so you'll nver see the 90+ game stages you see in IPSC. No RACE guns allowed! No comps either. Just what you carry on the street. ALWAYS must draw from a cover garment. Don't care if it's in the 90's in July. You only have to wear a cover garment while you're shooting. Both reloads and holsters must be positioned behind the seam of your pants. Insures concealability. We often draw our courses of fire from local news stories. Our course designers are graduates from the Marquis De Sade school of design. At least that's what we are all sure of....but the requirements are challenging and always throw new factors into the mix. We usually have a "BLIND" stage where we put up visqueen plastic and shooters engage the targets inside a funhouse without a walk through, first. We often do these at night with a flashlight. GUN LIGHTS are forbidden in IDPA, which I think sucks, but that's the way it goes.