I have not owned a DR and have only shot lower powered DR's at times, but I have certainly used some old poorly stocked SxS shotguns over the years which have booted and kicked me around particularly when only a youngster. Out of this I have never ever experienced a double discharge, although I would have thought some of those old 12 bores would have been pretty worn in the internals and most likely to due to mechanical failure.

Like a few on this post have indicated they do, I tend to use a fuller trigger finger contact on any firearm I'm using. My current single trigger O/U shotgun allows me to quickly select barrels with a flick of the thumb to suit chokes and cicumstances when hunting wildfowl so do accept the usefulness of a double trigger DR in being able to select bullet types (SP or FMJ).

I'm not sure that I could master using a rear trigger first then shifting to the front trigger on a DR particularly if facing a charge or a situation requiring getting two shots off in a hurry with out having to think about the process. I imagine for most DR or DB shotgun users with double triggers the natural process, when under stress anyway, is front trigger first then dragging back to the rear?