Just got mine and had it out on the weekend. My first mod will be loctite on the tube selector switch. Not a surprise, I had read online about others with the same issue of it working loose.
Tried 3? different types of birdshot/target loads and some Fiocchi 00buck through it. 300+ rounds in total. I think it needs more breaking in; even with full range of motion and forceful racking of the slide it did not always cycle smoothly. Issues were ejection and feeding related but with the cheap target loads I was expecting it, again after reading of others with the same problems.
I think if I had to go into combat today I would choose my Norc 870 clone, at least until I can get the KSG running reliably. Definately keeping an eye on this thread for ideas on mods.