i put the $90 cheapie on, took about half an hour, most of which was spent looking for a clean place to mount the box. No perceptible difference, really, except for not having oily points. Timing can be either done rigorously by putting a degree wheel on the crank, etc; or by ear-ball, which is what I did. advanced it until the idle speed stopped increasing, then pulled it back a bit and went for a ride. No tinkling even under load at moderate rpm, so that's where it stays.
I mounted the box upside down under the regulator, using the same screw. Very neat, nearly invisible, good cooling flow.