I like that little Kel-Tec. There were some problems with them in the beginning but that seems worked out now. Mine has been 100% reliable out of the box but did a quick "fluff and buff" just for good measure. It's a cheap little gun that you won't mind knocking around. Get one in hard chrome and corrosion problems is a non-issue.
Sure, people will say that even 9mm is a marginal defensive round and .380 is right out, but I still wouldn't want to get hit with one. The small round in your pocket is better than the .45 home in the safe. The P3AT is small and light enough that you'll find yourself carrying it everywhere, either in a holster in your back pocket or just by itself in your front pocket. (Keep in mind that there is no safety on these pistols so I don't carry mine outside of a holster of some sort. Some say the double-action, long throw trigger is enough of a safety, but not for me.)
I run Cor-Bon DPX in mine as the numbers look about the best and the pistol was designed around this round. For practice it will feed WWB without any trouble. Regardless of ammo, the first round of a mag needs a little slap on the back of the slide to feed. I expect this to improve with use.
One thing these pistols are not, is fun to shoot. You won't go to the range and put 300 rounds through it. It's a harsh, snappy little thing. I'll usually empty two mags through it just to keep in practice, then switch to something a little more comfortable!
Kel-Tec has a pretty vocal and committed message board who's members are always willing to answer questions. Poke around and you'll find a ton of information about these P3ATs and others.
http://www.ktog.org/
That holster is made by KD Holsters in Florida. There's a pretty long wait but it's worth it.
Kel-Tec also has the new PF9. It's a is a single-stack 9mm that's not much bigger than the P3AT. Again, I'm sure it's not fun to shoot but it would be nice to have a true pocket 9mm.
And for what it's worth, Ruger just came out with an almost exact copy of the P3AT that will be for sale this March. Really, it's so close to the Kel-Tec I can't believe they're getting away with it. Check it out. Ruger LCP.
And yes, I'm very interested in the Kel-Tec Sub2000. Because of this and other forums (and Easy610) I now own a Glock 19. In fact, I haven't even fired it yet. The next addition will be a Sub2000 that takes Glock 19 mags.
jim