600 rounds through my PX4 so far.
I like it. I've never shot a Cougar, but the recoil impulse on these rotating barrel guns is surprisingly manageable from a follow up shot perspective. The trigger is nice, both SA and DA and the gun handles very well and points naturally for me.
I'm going to plan on shooting the bejeezus out of it, and am tracking carefully the number of rounds of various ammo I'm putting through it.
One of the coolest things, in my view, is that the magazines have rib indentations so that the cartriges are contacting only the ribs inside the mag, instead of the entire "side" surface of each magazine. That should make these mags less susceptible to dust / grit failures.
I like my PX4 alot. Can't wait for the .45 ACP version, frankly.