As a defensive weapon it has long been obsolete. Compared to a carbine AR you are looking at a heavier, more awkward gun with limited range and ammo capacity. You are also looking at almost 30 ft lbs of recoil vs 4-5 ft lbs for an AR.
Perhaps with conventional shotguns, but there is the AA12- full auto, reduced recoil, 20 or 32 round magazines. Empty weight probably isn't that much more than an AR with the extra crap bolted onto it (32 rounds of 12 gauge is a bit hefty though). For certain urban warfare applications, I would think something like that could be quite useful.