I looked at both the CM9 and the Nano after the Nano came out.
I didn't like three things about the Kahr CM9. It was a silver slide and I much prefer a black gun for CCW for lower visibility when you might have to draw it. (I know that the Kahr PM9 does come in black and has two mags, but its price was just outrageous). The CM9 came with only one mag and the Nano came with two. And even though the Nano doesn't have an external slide lock, (it does lock back after the last round, though), I do like its very smooth profile. And there is a workable procedure for clearing a round if it does jam.
Both of them have seemed to have some issues regarding functioning. Some Nano owners have had a problem with low powered ammo, like WWB. But the Kahrs are famous for their break-in requirement of 200 rounds. I just don't agree with having to "break-in" a pistol that should function properly from the factory. And even though I am sure a lot of Kahr customers have had a good experience, I have seen some reports of Kahrs not being very reliable as well.
So, I took a chance on the Nano. And I have been very pleased. No problems yet and I have had it for over two years, including using WWB. And I really like it. It does have a heavier trigger than a Glock does, for example, but so does the CM9. And I am used to it.