I've owned and carried a PM40 for several years. $399 for one in good shape with 2 mags and box is not bad. Kahrs tend to be quite pricey (hence their CW bargain line coming out a few years back). I think that's what I paid for mine way back when (deputy from a neighboring county bought it and traded it back in after shooting TWO ROUNDS ... heh ... wimp). I mostly used mine as a BUG to my then-duty weapon and toted it OD a lot. Mine is an older model and I eventually had to replace the mag catch to the newer version (after I e-mailed Kahr one of their gunsmiths sent me the new catch for free and offered to talk me through the installation but without help it took me about 5 minutes including opening the envelope). I don't think mine has ever failed to go bang or cycle. That said, any of these little guns with power levels out of proportion to their size and weight (to include itty-bitty .380s) come with some special considerations:
Hold it like it's a snake that wants to bite you and if you have any cycling issues, try shooting it one-handed and see if the problems go away. Yeah, I know, I know, but these are not target guns or duty guns, they are easily carried, powerful little "Get-Off-Me" guns. A lot of our favorite two-handed grips actually leave a tiny spot unsupported on the backstrap due to the minuscule size of the grips. This means the gun moves a little more under recoil. It's vitally important that you hold on tightly and minimize how much the weapon moves under recoil. They really depend on your hand and arm soaking it up. Usually for my tiny pocket blasters, if I shoot two-handed I have to use the old now frowned-upon "cup and saucer" hold to ensure reliability. Shooting tiny guns like duty pistols often, in my experience, can lead to functioning problems.
None of that will be a problem once you realize the situations in which you're most likely to draw and fire may well be one-handed, toe-to-toe, very fast engagements.
Mine has the XS express-style sights. The tritium has faded to quite dim over the years but that big ol' dot is sure easy to put on target and drop into that shallow rear groove. My old agency's BUG/OD course required shooting from 15, 7, 5, & 2 yards, 25 rounds total. I never had a problem qualifying, in fact I think I always shot 98 to 100%. It's not (for me) a fun shoot-all-day gun. Half a box and I'm pretty much done with shooting it now days (arthritis). The Kahr I mostly carry these days is it's smaller brother the CW380. But it still gets a lot of carry time still, especially in the summer when bigger guns are harder to hide. If you get it, enjoy it! Kicks like catching a line drive bare-handed but they put an even bigger hurtin' from the other end, too.
p.s. At a ballistics seminar the agent teaching the course shot my PM40 (165 gr Federal HST) into the same gel block (t-shirt covered) that he shot a 180 gr HST from a Glock with a custom 6" bbl. The rounds wound up side-by-side at the 16" mark, and you could not eye ball any difference in the rounds; both fully expanded with nice wound tracks. --- Take that for whatever it's worth, but I took away from it that the short bbl doesn't rob a lot of performance from the .40 S&W round.