My PT-111 (non-PRO) has had zero failures of any kind in over 2000 rounds. It was my primary carry gun for more than 5 years until the day I picked up a Kahr P40 and fell in lust with it. The 111 is still my backup gun and will always be found within arms reach in a map pocket, desk drawer, or other easy-to-reach spot.
As others have said the 111 is not a tack driver. At best it's only accurate to about minute-of-badguy, which is perfectly acceptable given the defensive purpose of the design. The loooooooonnggg trigger pull takes some getting used to, and is unforgiving of shooters who jerk their shots. In fact, I've used it to on several occasions to teach "jerky" shooters how to squeee-e-e-e - e - e - ze the trigger. When they got to the point that they weren't pulling shots on the 111, I transitioned them back to their own guns and they were amazed at how much more accurate and precise their shot placement was.
One of the best things about the 111, especially from a defense standpoint, is the true second-strike capability. Although it's rare these days, it's still possible to get a light strike or hard primer. It also means that there is no tension on the striker until you pull the trigger so, along with the striker block and manual safety, it would take an extraodinary (and statistically improbable) string of events for the 111 to fire without the trigger being purposely pulled.
It's not a perfect gun by any means, but it does make a dandy defense gun that doesn't cost and arm & leg and goes bang every time.
Brad