I have installed the TT fork cartridge on my 2019 F850GSA. This bike typically has 30 to 40 lbs of luggage and I am 6'4" 2020 lbs. I live in SW Idaho, near Boise and have the opportunity to ride forest service and logging roads out my back door. The Idaho BDR passes by about 30 miles east of me. The bikes front end was a bit soft for my liking off the show room floor but worked well on the roads I like as long as I was gentle on my brakes. When I needed new fork seals, it seemed like a good time to consider the TT upgrade. I purchased it from the Beemer shop and had the local dealer install it. The money I saved at the beemer shop paid for the installation.
Riding: this cartridge is fully adjustable and the Beemer shop set it up with the right spring for my weight, so I have for the time being left it as it came out of the box. It has made the bike a bit stiffer riding washboard, but also has made fork motion much more predictable and controlled. Riding through pot holes, ruts and rocks the bike feels more planted and controlled. Stopping: Hit the brakes hard, the nose doesn't dive and you stop almost level.
I feel that BMW on their premium package should have the TT cartridge as standard equipment on the F850's