I've only seen one. A used one at a gun shop. Seems fairly solid, but there was some play where it folds up. Maybe the one that I saw was rough handled.
Way late on this review but a buddy of mine picked one up not too long ago and liked it for what it was. Says it was pretty accurate too. I haven't shot it yet...
Back at our LGS, they had and only ever sold 1. Feedback was, way too much plastic, hard trigger with no upgrade options. To me, it's too Tacticool for my tastes. If I were looking for a pistol caliber carbine, I would look for a used Beretta CX4 Storm in 9mm. Sure it's more expensive, but you are getting a million times better carbine than a Kel-Tec. And it will also accept PX4 Storm magazines if you also own one.
Or a Kriss Vector CRB with TacPac in .45 ACP. Semi auto civilian version.