I own, or have owned several Kahr pistols, with excellent results. I recently swapped for a K-40, even though I have avoided .40s previously, believing that 9mm and .45 ACP are both more sensible rounds. I still think that, but I have warmed up to the .40 S&W a bit, since acquiring the K-40.
Make no mistake...the K-40 is a handful with 180 grain self defense ammo, but very manageable with a proper grip. I would only recommend it to folks who are experienced handgun shooters, because I think a novice would find it unpleasant enough that they would anticipate recoil and likely not want to practice much. Personally, I enjoy shooting it, but 50 rounds is plenty for me, in one session. Mine shoots 2" low at 10 yards, but groups tightly, so I will likely replace the sights with three-dot night sights. Also, I may, at some point remove the Crimson Trace laser grips from my K-9 and put them on this one. I will shoot it a few more times before deciding about the sights. Meanwhile, I'm good with aiming a little high to hit the bulls-eye.
As for a carry gun, I think it is a perfect IWB handgun. It is fairly heavy, but less so than a 1911 clone or most double-stack polymer framed guns. Most importantly, it is a powerful gun, suitable for self-defense against human predators. I am a large guy and have no problems at all with the weight of the gun, with a good belt and a comfortable home-made leather holster. I've been carrying mine in the Texas heat for about a week, now, and far from being comfortable, it is bearable...which is about the best that can ever be said about carrying a legitimate personal defense handgun, concealed, during hot and humid weather.
My bottom line for recommending the K-40 is this: Most folks would be happier with the 9mm, and loaded with hot 147 grain hollow points, it's just as good as the .40 S&W, for all practical purposes, loaded with a similar bullet. One mm ain't much difference, so to gain an advantage by going .40 caliber, you need to jump up to 180 grain bullets. It is not a 'newbie gun,' but not bad for an experienced shooter.