I have the G17 Kel Tec and the only major beef I have is that the front sight is pretty cheesy and hard to get adjusted really well. My gun was bought for $300 + tax some years ago and the orange sight blade is held in with a screw and nut...you loosen it up and the orange blade drifts up and down and you have to futz around backing out and tightening the screw and nut both to get the windage set. I adjusted my gun to fire the 147 grain 9mm ammo. Another issue is that Kel-Tec says not to use aluminum cased ammo - so the inexpensive CCI Blazer is not usable. Kel Tec didn't make any effort to allow an owner to easily put a red dot scope or optic on the gun, and if you do rig some way, you lose the abilty to fold it in half, which to me is one of its selling points. Really makes it portable and stowable folded. I keep mine in a small nylon bag in the car trunk. It really rocks with the 33 round magazines!
FWIW, I do like pistol caliber carbines. My favorite is my Marlin Camp Carbine in 45 ACP, second favorite is a Marlin lever action in 357/38 special, then comes the Kel Tec.
By all means, at some point get a Ruger 10/22. It is hard to beat a good 22, a brick of ammo and a fun afternoon at the range or out plinking