It had the sloppiest slide to frame fit of any new gun I have ever owned and was punishing to shoot a lot.
If the slide/barrel fit is right and you use the sights, a sloppy frame/slide doesn't matter all that much. (There are some tack-driving guns with sloppy slide/frame fit.)
But, as you say, the PF9 (or P11, for that matter)
can be punishing --
but that's what you get with a small, very light gun firing a 9mm (or larger) caliber, and the PF9 is one of the smallest, lightest 9mm semi-autos you can find. (The Rohrbaugh R9 is smaller but a bit heavier; while I haven't shot one, I'm told that it's a handful, too.)
(The Kel-Tecs have an aluminum frame rather than a polymer frame -- and while the polymer covering makes it look like a Glock or Kahr, there is none of the "flex" in the frame you experience with some of the polymer-framed guns.)
I prefer shooting the small Kahr to the Kel-Tec (I have both), but have gotten comfortable with the PF9 and don't know whether I'll eventually switch to the CM9 (or maybe a PM9) or not.
A while back I found some grip materials from KTADDONS that made a big difference in the shooting experience. Most of their stuff can be used with other small guns, too.
http://www.ktaddons.com/index.html
A surprising number of folks try this type of gun as their first semi-auto, and that's arguably not the way to start. <grin>