I can speak for the KA crowd, several KK owners I know, and myself.
Preclude: I was not comped my lift. I paid for it! I get no $ from JBA if someone orders a lift from them. I recommend their products because my lift works great, is high quality, and I would have nothing less on my ride. It's been 10 years with my 2.5" lift with ZERO issues.
My rig (KA) was used to prototype, test, and develop the 2.5" lift for the KA(which is the same lift the KK uses). I am not near JBA so we had to work together long distance. I'm in WA state.
We went thru several different revisions and tested several variations of components(springs, A-arms, shocks) during the development phase. During that whole time the communication was great, and support was above and beyond.
During the process there was one period when communication was slow, but at that time Marlin was ill, so I can't hold that against him or the company.
All the parts that were sent to me arrived with no damage. Total parts would be = to 3 complete lifts. Parts that did not work were shipped back on JBA $.
Once we had a component setup that worked, JBA started selling kits.
During this same time Diggerfreek from here on Lost was working with Marlin to develop the KK 4" lift. Digger and I talked a lot during this time. He related a similar experience with Marlin and JBA as I had.
Speaking for the KA crowd, I know numerous KA owners(from in the US, Canada, and abroad) who have ordered from JBA, and there was only one issue I have heard about. A set of KJ rear springs were shipped by mistake. Correct replacements were shipped and arrived in 3 days.
Now most KK owners don't know this, but the KA was made in 07 and in 07 the KJ was still produced. The issue with the rear springs was a rig clarification problem. On whose part I can not say, but JBA made it right ASAP.
The testimonials here on Lost can talk for the KJ and KK crowd.
To the OP of this thread, I wonder who is running the KK Facebook group? Is it a competitor of JBA? That would explain a lot.