I installed the sprint booster on my 2018 4R about 3 months ago, I did the proper installation where you open the door and wait 10 min, etc.
No issues at all so far.
One thing I noticed that I did not see in the reviews, besides the faster throttle response, the 4R upshifts faster if I push the gas pedal a bit more, like if I want to pass a car, or speed up on the highway.
Before, I had to push the pedal quite a bit for the 4R to upshift, and quite often it would upshift 2 gears or more - the engine would all of a sudden rev very high and the 4R would jump forward.
With the sprint booster it is much easier to control the upshifts.
I set it to green level 8. The red is waaaaay to responsive and hard to control for me.