I would have answered earlier but was put off by the server change.
I have a P-11 as well as a P-40 (the 40 S&W version). I carry them as a back up to my duty weapon or when I absolutely cannot get away with wearing a full sized pistol. As mentioned, they have a rather heavy trigger pull (9# on both of mine) though there are means of smoothing it out that makes it seem lighter while keeping it reliable. I found the grip to be a bit short for me but a magazine extension did the trick as well as adding a round or two to the capacity.
Overall, they are dependable guns but I would question their longevity if fired a lot. Their small size is a deterrent to that but I replace the recoil spring every 500 rounds on them rather than 1500-3000 rounds on the standard guns. I have never used Kel-Tec's customer service though the Kel-Tec talk group seems to have spoken highly of it when I frequented that site. that is where I found the info on trigger work and other modifications one can do to the gun.
As for the value, I don't think it would be a good trade between the M&P and the KT but I do have a Jennings/Bryce 25 ACP I will let go even up if you are interested. That would be a better trade for me, er you, I mean us.... If i were to be buying this gun I would look for a price someplace between $200 and $250 for it. I bought the P-11 a couple years ago for something like $190 while the P-40 ran closer to $230 a year before that. Then again, the P-40 had been discontinued and there was an unreasonable demand for the gun at the time. Today, I would hope to get $250-$275 for the same gun with the mag extensions and modifications so $275 may be a bit much if it is still "stock."