I have the PX4 9mm and have the following observations.
At about 2500 rounds, one of my 20 round magazines inserted into the gun and the 1st round nose dived into the frame. The same mag did it again the next range session, and 17 rounder that came with the gun did also.
Diagnosis: Bad magazine springs. I called BUSA, they provided a way to test, I did, and confirmed. Only 2 of 5 magazines have this problem.
At ~3800 rounds I had FTF with WWB, in fact the round would not chamber under tap/rack/bang SOP so I removed the mag, cycled the slide about 3 times and the round fell clear. I retrieved the round from the floor and it was unscathed. Visually it was normal appearing and in comparison to the other rounds it was virtually identical. Locking the slide to the rear and loading that round into an empty mag, the round chambered. Loading it back into the original mag on top of the 16 remaing rounds, it chambered again. It fired also as did all the other rounds that night.
Diagnosis: Unknown cause.
Incidentally, from the same "batch" of WWB, purchased at the local Walmart but a different box I noticed that the recoil was quite pronounced. I retrieved several of the spent cases and these rounds were cratering and dimpling the primer showing signs of overpressure.
I'm not sure what the service life is *supposed* to be on the PX4 magazine springs but in any case I'm under 5k rounds through this pistol, so keep this in mind. It's possible that they were just bad springs to begin with but I've got original 92 magazines that I bought in 1990 that failed to lock the slide back for the 1st time in October of 2006. They had *never* been cleaned or so much as been in the same room as a gun cleaning product.
The PX4 is very accurate for a 'service' gun, easily on par with any of it's intended competitors. If you are comfortable with a DA/SA, then you may like the PX4 very much, but if double action isn't your cup of tea, then stick with the short single action triggers.
As always, YMMV. IANAL. TINLA. Etc.