I have a Mossberg 500 Turkey Thug 12 gauge with the lightning pump action trigger system...at first mine had a problem with the cartridge stop (it was bent to far out, not letting the shell get on the elevator), but after bending it slightly back, and reassembling/re-oiling it, now it works great.
I also own a Mossberg 835, and it's never gave me any trouble *knock on wood
Some people don't like Mossberg, but I am NOT one of those people. Enjoy the new gun :)