Build quality is uneven (mostly regarding the gas ports). Reliability isn't bad once broken in (they like heavier loads), but it isn't as absolute as the AK design rifles. Reloads aren't as fast and easy as you'd think due to the lack of a last round bolt hold open. It is a soft shooter, but I find that occasionally I have shells go nose-up into the top of the chamber for a failure to feed jam. That would be a problem in a HD scenario.
If you get one and it runs well, then it would work as a HD gun, but I'd sooner reach for my 870 for that, no matter how awesome the S12 looks.