They do have some fun toys. Who wouldnt want 20+ rounds of WMR in either an auto pistol or rifle? (And dont blame them for reliability. The first auto WMR was in the 80s and it was notoriously bad because that round is notoriously difficult to run a blowback system... took decades to figure out)
And their 308 that spits the brass forward out the tube under the barrel is neat.
Not that I would necessarily EDC one of their guns or trust my life with it, but they have fun toys.
Every Kel Tec I've owned broke. When they started getting snobby about their warranty and looking for reasons to deny coverage I was totally done with them. I now have a SCCY as a beater pistol and it's far more comfortable than the old P11s I owned.
I always got the impression that Kel-Tec existed to finance Kellgren's mad scientist lab where he comes up with these little pieces of weirdness, then he picks a few that seem marketable and manufactures them as cheaply as possible. I will admit to a sub-2000 and a PMR-30, but just for fun.
Kel-Tec makes some interesting guns but those multi-barrelled shotguns are a novelty IMO, nothing more. Unless your house gets broken into by the "Perfection Grab-oids" you're never going to be in a firefight that requires you to unload that much carnage. Not that we shouldn't be allowed to own it, just that to me its just something you'd have fun with at the range and get your friends ooh-ing and aah-ing over. I give Kel-Tec straight A's in the cool-and-unusual category but I don't think their KSG's are practical even for military use.
I don't have any firsthand experience with their products, and I have to admit that the RDB had me intrigued in the past. I think it is one of the better looking bullpups, but there is no way I would drop $1300 on one. Maybe if it were down in the $700-800 range.