While I haven't purchased one, I have had a chance to shoot about 100 assorted rounds through one. Would I buy one? Not at their current prices. Are they a viable HD firearm? Certainly, but you can get a shotgun that is just as good, plus ammo, plus training for the same price. That training will make you a more effective defender with a Remington 870 than spending all your money on the KSG.
KSG as a hunting gun? Nope, not a chance.
If the price came down a bit (if supply caught up with demand), then perhaps I would, but I am not too sure.