After doing some shooting with my carry gun and also installing a gizmo on my M&P357 that I'll maybe write about later, I pulled the PPX out yesterday to put another 50 rounds of Winchester White Box 115gr FMJ through it, bringing the tally up to 750.
I was standing at about 15 yards and ringing the steel, having a grand ol' time, trying to play a tune on the different-sized plates. When the second to the last mag went dry I did a speed reload from the belt pouch and...
Not sure I should hold shooter error against the gun. The unusual shape of the floor plates and magwell opening could take some getting used to for me.
ETA: Incidentally, nosing around the Walther fanboi sites, it appears that P99/PPQ night sights are compatible with the PPX.