I thought about it back in the day, but when I started carrying, I slowly went down in size until I got to the G27, then I went back up to a G29 when I could conceal it well. Now I'm considering getting a rig for my G20, but 2? Wow. That would be heavy and uncomfortable (for what I do). If I needed the firepower, I guess it would make me feel very comfortable.
Personally, if I do need that much firepower, I'll just grab the M4. The pistol is for shooting your way back to the rifle, right? I just built a new one, a pretty close copy of the one I had in the army, so I can throw the old one behind the seat in the truck.
I can see the usefulness as a bodyguard or whatever, as a civilian CCW, I can't really comprehend it. But that is part of freedom, you know? Do what floats your boat as long as it doesn't slow mine down. My biggest problem with it besides concealment and weight is that I am VERY right handed, to the point my left serves the right --usually with full mags. I'd need a third at least just to make it work.
Anyway, when the stuff goes down, I want one of you guys standing next to me, 1. because I'll let you return fire because you are way better armed, and 2. because you'll be weighed down so much, it will make it easier for me to run away while you cover me!