My experience of them is that they are big expensive kits. But, unlike some other big expensive kits they are well made, all the parts fit, and they work reliably.
I was once involved in terramechanics experiments with tracked vehicles. Due to the costs involved in using full size vehicles most of the work was done with "models". The first models, from a variety of sources, were hopeless. Poorly made and ran very badly. We spent more time repairing them than experimenting.
Then we discovered Armourtek. A revelation. No matter what we did with it it always worked, no broken tracks or failed drive line.
After the project had finished, successfully thanks to Armourtek the vehicle was used to demonstrate mobility of tracked vehicles on sand. Frequently overloaded and abused by students it never failed. As far as I know still going strong today!
John