I bought one but have not installed it. It's so cheap, it was hard to resist. And I'll bring along a set of old points/condensor in case it fails.
My experience is that this sort of thing usually fails early during "burn in" (hence the "infant mortality" comment above). If it lasts a few hours, you'll probably get decent service life out of it.
One thing I have done with the Pertronix unit in my race-Spridget (and will do with this): I'll run power to the coil through the resistor all the time (no bypass circuit for starting). Even with reduced current to the coil, my race car starts easily and, I believe, this acts as an "electrical cushion" that reduces voltage spikes during starting. My Pertronix unit has been in service with this arrangement for over 10 years.