Had one for a while
My experience:
Took forever to get it hooked up -- tons of adapters, connectors, hoses, etc. -- all potential leaks. Plus had to build a custom bracket.
Intake went into the oil pan plug so it was always screaming, "Drag this off on a rock somewhere!"
When it ran it was nearly as loud as the engine but a lot more annoying (more the frequency than the volume). Took it off and remounted on a second custom-built bracket that had rubber grommets to keep the sound out of the frame -- only a little better.
The pump leaked all the time -- constant drip right out of the pump itself, not the fittings. Remounted it so the leak wouln't run into the motor -- really got tired of cleaning that up.
Oil analysis before & after indicated the pump added more iron to the oil than the engine did -- sure made it hard to identify any benefit.
Took it off first chance I got -- threw it in the trash -- wouldn't even give it away, much less try to sell it.
Kept the timer module -- might be nice if I ever need to power a circuit for a time after another circuit shuts off -- still can't think of what that might be.
It's a good idea. I just haven't seen anyone implement it well.