From the Kel-Tec website: The .40 SUB-2000 can be configured in the following magazine types: GLK22, GLK23, BERETTA96, S&W4006, SIG226.
It's an interesting concept. It's small enough to store in a briefcase, the center console of some cars, or other relatively small areas. It shoots fairly well and is fairly accurate although Kel-Tec had some problems with the front sight being canted to one side. I think they may have fixed the front sight issue but you might end up with a "new old stock" gun and, if you do, Kel-Tec has been good about fixing it.
I ended up with a bruised cheek when shooting it because, to get a good sight picture, you need to rest your cheek on the metal tube extending to the butt stock. That could be easily solved with some padding on the tube. I was able to regularly hit an 8" steel plate at 100 yards off a rickety rest so, at least from my perspective, it had reasonable accuracy. There were zero reliability issues (i.e. FTF, FTE, etc.) in about 300 rounds.
You ask if it's worth it. Well, it's not terribly expensive. It seems to be relatively well made for a plastic gun. It's an interesting design and engineering. It seems to be relatively accurate and reliable. It has interchangeable magazines with popular pistols. Some would consider it a toy or a novelty. Others would say it's a good bug-out or zombie gun or some other semi-rational explanation for owning one. In reality I suspect most of the firearms we own are used for leisure and are not necessary (don't tell our wives)? So, I would say it's worth it.
John