I bought a brand new PF9 in early 2011 after getting a decent deal at my LGS. With range test firing it had issues off the bat.
The factory magazine when fully loaded would not chamber reliably into the pistol. Unfortunately it only came with one magazine so i could not test this issue with another magazine, and no other store had one in stock.
I had double feed and stove-pipe issues using WWB and Federal ammo. I learned from KTforums that the feed ramp needs to be polished. The ejecting issues were bothersome too.
The trigger pull is long, which is normal for a pistol in this class. this makes double taps kind of hard since you have to let the trigger reset all the way for the next shot. There is also very little room for your finger inside the trigger guard, which can be a problem for those with larger fingers.
Sometimes I would accidentally press the mag release, partially ejecting the mag by a few mm but not drop the mag. This can be a personal issue, but I've never had this issue with any of my pistols (M&P, XD, 709/740, Glock).
If you are lucky enough to get a working and reliable one, then it is a great lightweight pistol. I carrried mine for about a month before selling it. I really wanted to like the PF9, but the issues prevented me from doing so.