As I have said in earlier posts, the PM9 can get rimlock. It is something about the top round and the next round in a full mag jawing away from each other, causing the case flanges to hang up. This is also true for the replacement mag Kahr sent me. Based on what I have read on THR, most people will not get this problem since they are using the PM9 as range gun.
I have not yet read one post on someone using the gun for self defense, which would involve chambering a round from a magazine that had been jostled around awhile.
I own both a PM9 and a Kel-Tec PF9. I would not compared these two guns in sturdiness - the Kahr is much more solidly built (you get what you pay for).
The PF9 is already getting significant wear on the slide rails (the aluminum insert into the plastic grip) after 50 rounds. Raw aluminum is clearly exposed and a lot of it has been washed away (similar to a photo I saw of a Skyy gun on THR).
What these two guns do have in common is that for some reason I cannot hit the side of a barn with either. The Kahr is very "jumpy" when fired (and the sharp grips can cut your skin), and the Kel-tec is both jumpy and slaps the hand very hard. I have big, strong hands but my shots with both guns always go way high.
If I had to do it over, I would not have bought either gun and just gotten the G26, which I have now. It is very accurate for me and more powerful than the other two guns. It is also better built than the Kahr by a significant margin.