My Kel-Tecs have been flawless. I have a P-3at (second generation), a PF-9, and a SUB-2000. I have fired over 5000 round with out a hiccup since I broke it in. The PF-9 has had over 2000 rounds and flawless (didn't even have a problem during break-in) and the SUB-2000 has had over 7000 round and still flawless with it.
From what I have heard is the first generation P-3ats were a little glitchy, but were better after doing a "fluff and buff". Check this link for more information. Link Removed
There was some changes to the second generation, and that seamed to have fixed most problems. I have not fluffed or buffed mine and as I said, no issues. Just like buying a car, your mileage may vary.
I used FMJ during break-in (Kel-Tec recomend using 50 round for break-in, I when 100). After break-in I fired 20 round of the JHP that I carry for Self Defense to make sure that they would feed. This procedure is what I have used with all of my firearms.