I have mixed experience, both with my Walther PPS M2.
I got their kit for the 6 round magazine last summer. I've put at least a few hundred rounds through it and have never had a problem.
I recently got another kit for the 8 round magazine. This never had any problems feeding or during actual operation, but twice I had issues when unloading the gun at the range. When I ejected the loaded magazine, I saw that the top round was kind of nose-down in the magazine. When I pushed it out, the rest didn't follow and just rattled loose. I could freely dump them out of the magazine and then saw that the follower was stuck down at the bottom of the mag.
Happened on two occasions. But I ran 300 rounds through it overall and had no failures during operation. Still, I contacted them and they exchanged it. I just got the new one yesterday and will install it. Customer service was fast.