I have used it!
Whether it is worth it it SBR your pistol is an individual thing. It is very well made, reliable, and super fun to shoot. For most people who are not in an LE or security work, it will be a fun toy, or part of their collections. Many will use it for home or vehicle defense. So it is a simple matter of deciding if it is worth the cost to you.
Apparently many think that is is worth the money for them, since it is one of our biggest sellers, and received a lot of attention at this years SHOT Show, not just from law enforcement, but from individuals.
Some people seem to have a real hang-up with the idea of SBRing a pistol, but the same people have several SBRed ARs or other rifles. There is no difference between SBRing a pistol or a rifle.
Here is what it does:
Gives you a carbine in a package smaller and more ergonomic than a Micro Uzi.
Increases stability for better accuracy and increased effective range.
Does not require permanent alteration of the pistol.
Allows easy mounting of optical sights.
Gives repeatable accuracy.
Is super fun to shoot.
What it does not do:
It does not increase the ballistic effectiveness of the pistol. If you need the ballistics of a rifle cartridge, this is not the answer. If you already have a rifle or carbine, and want something different, why not? If you need the compactness and concealability, the KPOS is the answer.
Advantages over similar systems:
The KPOS was built from the ground up for serious use. It is made of aluminum and steel.
The KPOS is much more compact. Compactness is why it exists. Rifle-sized collapsible stocks and bulky polymer construction defeat this purpose. If the system is too big, it would be better to just SBR an AR-15.
The KPOS does not cause carbon buildup in the front of the slide and barrel which can cause malfunctions. This is an issue with other such systems.
The KPOS has a built in safety system that covers the trigger.
The KPOS does not interfere with ejection. The other systems have brass deflectors that sometimes cause malfunctions by throwing brass back into the action.
The KPOS works well with most suppressors.
The KPOS allows use of the pistol's iron sights should the optic become disabled.
The KPOS actually positively supports the pistol's frame at both the front and rear - the pistol is not just sitting inside.
The KPOS conceals under a light jacket or windbreaker. The entire system will fit in a pistol case.
Hopefully we will can get some comments by others who have used it. Just be aware that there are some who will always just attack a system like the KPOS, and others who have other systems who will attack it even though they have never used it. We find that most who comment on any of these systems on forums have never actually used one.
Hopefully I was able to provide some info to help you decide whether it is a good choice for you or not. Ultimately it comes down to your personal preference.