IDPA is fun, but it is fantasy!
First, the "assailants" aren't shooting back. Been there, done that with Iranians on motor boats before everyone and their cousin served in the Persian Gulf. "Fully reactive targets" shoot back. Then you find out what every cop or combat veteran has ever found out when being shot at: Manuevering is overrated if you have good cover and don't have to expose yourself to return fire.
Having been shot at by Islamofascists while hunkered down behind a pintel mounted Ma Deuce, with a steel plate shielding it, gives me a large amount of appreciation for infantry and cops, two groups who might have to manuever under fire. My only taste of having to clear places with even potential hostiles was in ship boarding in international waters and that is gut wrenching even when nothing happens. People who have to move about under fire or clear an unknown space with potential hostiles, have my utmost respect of their courage. Knowing the feeling, and knowing that the whole world sucks at that moment when shot at, my preference in a hold-up or "street confrontation" will be to dive to cover if it is available, draw, and stay there unless I can't. I'll draw and fire without cover if I need to save myself or a loved one thank you very much, and then get to cover, but not manuever just because there are targets in the area or because I gamed a scenario just like this one once or twice during a shooting game.
Does any of my admittedly little experience with warfare translate to my civilian shooting life? I tend to think so, especially when I participate or watch range activities. Several observant people have pointed out what I already tend to think: Gaming reloads and weak side shooting or shooting many "perps" in a stage is a load of BS. Sure, someday someone might get to play the role of The Punisher, but it is exceedingly unlikely.
In the real world there will not be any pop-up steel cutouts waiting to be neatly double tapped in the A-Zone or Mozambiqued. Contact distances will likely be way shorter than the 15 yards I see many people practicing against. I often see, and I'm even guilty of it myself, more time spent banging away for giggles or tighter groupings and not enough practicing a draw and first shot or two. For that aspect alone, IDPA is worth something.
However, let's not confuse the artificiality of the tactical scenarios in a game, wherein no one tries to break contact, the good guys all play Bruce Willis in Die Hard, the bad guys are almost always attacked one at a time in a scripted stage, and their inanimate morale always holds long enough for you to have to perform a "tactical reload," with real life.
I'd feel perfectly fine with a five-shot .357 Magnum revolver. The chances of anything more than presentation or "brandishing" being required are vanishingly small, and if the weapon needs to be used, there would be enough, with one reload, to get anything done you are likely to survive, alone, weak-handed or otherwise.