The first time I installed a cruise I used a vacuum unit that cost me about $150 for the unit, then had to build a vacuum storage unit and put vacuum fittings on 2 intake tubes. Cost was under $200.
This one worked amazingly well. It kept speeds within 1 mph approaching inclines, at the top then going downhill, rolling hills, headwinds, didn't matter it was right there.
Unfortunately it suddenly quit one day after some surging and dropping off. My guess is where I had the main unit installed inside the fairing lowers right behind the radiator cooked it.
The Rostra I have now works but not as good.
It seems to take a good 5 minutes or so to adjust itself before it keeps speeds reasonably stable but even then nowhere as stable as the vacuum unit. I have played with the settings every which way from Sunday, finally settled with the way it is.
For anyone thinking of installing a cruise I recommend a vacuum unit hands down. It was pretty much plug and play with no fiddling, just install it away from heat if possible.