I've put 700-800 rounds through my Kriss non-restricted and haven't had a single failure to fire or failure to eject. The thing runs like a dream. The ammo I've used so far is:
Remington UMC, 230 grain, FMJ
Remington Golden Saber, 230 grain, JHP
American Eagle, 230 grain, FMJ
Hornady Zombie-Max, 185 grain, polymer tip hollow point
I've spoken with the guys from Kriss USA at length and they admitted that the gun was probably released too early. Some of the kinks hadn't quite been ironed out when they released them to the market for sale. But the newer guns have been produced without problems that dogged the early models. Charlie Martz, Kriss' chief gunsmith, told me that he likes to run his pretty wet. So if you buy a Kriss, make sure she's got a good lube on'er, use the approved ammunition and don't feed it crappy ammo, and you'll have a ton of fun.