I was immediately drawn to the size of the Kahr's, especially since I view pistols primarily from a CCW standpoint. Since they are small, thin (single stack) pistols, they seem ideal for concealed carry.
However, my experiences with them have not been that great. I've owned a K9 personally and have two brother's who both own PM9's. At times I've had a hard time getting through an entire mag without a failure (or two)... They have been sent back to Kahr and they remain unreliable.
Some people believe that the steel framed Kahr's are more reliable, whereas the polymer framed series are the troubled ones.
The K9 I had was hit or miss with reliability. It would shoot just fine and then begin jamming up every other round for no apparent reason. My brother had a MK9 that I don't recall ever having too many issues...
They make accurate guns, it seems. However, the trigger pull on these pistols is extremely long and really kind of annoying.
In the end, I can see the appeal of these guns, their size makes them extremely attractive. But they simply do not perform in my experience.
UPDATE (11/24/09) - Recently I went shooting with some new friends of mine and was able to try out a Kahr CW9. We all had the chance to shoot a few mags through it and to my surprise it was 100% throughout the course of us shooting it.
I am not quite sure what to think. The jury is still out it seems. Maybe he just got a good one, but his worked just fine and kind of made me feel bad for all of the bad things I have said about Kahr. But then again, my K9 was reliable at times too, and would suddenly and inexplicably start having issues. He claims that it has never really given him problems. Maybe he just got lucky?