I had the fortune to shoot a Kahr CW9, which is quite comparable (size-wise at least) to the Kel-Tec PF-9. The Kahr weighs in 17.7 ounces with the clip, which is five ounces heavier. Dimensionally, the guns are about the same size, just a little different shape. The Kahr is on top, the Kel-Tec is on bottom.
Shooting the Kahr was much more pleasant than the Kel-Tec (or the Ruger LCP for that matter). I think this is due to the somewhat longer grip, and the extra weight. I found the sights to be easy to read, and the gun accurate. I can't really comment on the grouping, since I only shot one or two clips worth.
I will say that the Kahr has a much better feel to it than the Kel-Tec. The recoil is is more manageable, but more importantly is the quality of machining. The obvious differences are that there is no seam in the plastic, and when you release the slide, it just feels better. The gun only had about a hundred rounds through it when I shot it, but everything was very smooth.
All in all, I liked the Kahr in terms of quality. It also was more comfortable to shoot. The extra weight is definately an issue for carrying, but could be partially mitigated by stepping up to the Kahr PM9.