I installed my Rostra over the winter and have tested it on three rides. It has some quirks and doesn't work as seamlessly as the one in my car, but it does the job.
The routine that seems to work best is to turn on the device, wait a few second for it to wake up, then hit the set button. Next, I hit the resume button and the thing begins to function. Without hitting the resume button, it may or may not kick in.
The CC is supposed to allow you to accelerate to a higher speed and then return to the set speed, but mine just kicks out.
I find it a bit of an odd experience to feel the throttle turning by itself in my hand.
Overall, I'm pleased with the CC. It'll make life easier on those long slab days.