The problems reported early in the series II release had to do with the free floating "push rod" in the frame being over-long and (IIRC) on the compact guns, it would/could be induced (firing the gun inverted) to jump up under recoil and impede the slides forward travel, leading to a failure to return to battery.
Its not a failure to be taken lightly but I believe it has been adequately addressed by Kimber as the series IIs moved forward, and is an issue than can be completely resolved by removal of the series II components.
Alternatively, one can simply swap the firing pin for a series 70 pin, and remove the push rod from the frame.
I prefer complete removal and have done so on the three series IIs I own.
BTW, the Glock firing pin safety is a bit different in design, and couldn't prevent a return to battery without a serious parts issue, because the trigger bar drops down at firing and the ramped portion that presses the firing pin safety plunger up shouldn't be in contact with the underside of the slide.
The Colt Series 80 system uses a lever that rises at the front, so the slide wouldn't be held up by it either.
I'm not impressed with the Kimber system, and wonder, among other things, why the mass of the plunger is so great in relation to the "push rod" that deactivates it.