Mine is ammo sensitive. I have maybe 400 rounds through it at this point.
On Monarch (Academy brand) 40S&W, mine will jam about every third or fourth round. It just doesn't seem to have enough energy to reliably cycle the gun. This ammunition works fine in my Hi Point JCP .40. The Storm does seem to shoot fine with Winchester and other stronger loads. It also has a good, quality, feel in the hand, seems very well built, and is easy to strip and clean.
I just got into firearms at the end of August, and have bought about fifteen or sixteen handguns of varying quality levels since then. The Px4 Storm .40 is my least favorite. Maybe I just don't like .40. The Storm and the JCP are the only .40's in the bunch (so far).
I have a Px4 compact in 9mm (wife's) and a Cx4 carbine in 9mm and like those just fine.