Lots of real world experience posted on CF. Do a search.
I've had three over the years:
1. Windbugger, good output, old technology, high
maintenance. Now out of production. (ten years with this one)
1. KISS, simple, good output, low
maintenance, manufacturer provided
parts list available from automotive stores. (nine years with this one)
3. D400, complicated, heavy unit, amazing output. Expensive. ( Only used it two winters so far.)
All above units don't put out much (under 4 amps) under 10 knots. Between 20 and 25 knots they perform best except the KISS gets hot and the thermolswitches? shut it down. The D400 goes on forever but as I said is complicated with a charge controller and resisters to dump the load. The other two units have no charge controller and rely on the operator. I never left them on when not on the
boat but with the D400, I leave it on all the time. Also the D400 is surprisingly quiet. The Windbugger was the noisiest but much quieter than WindMarines. With the D400 I miss the
noise when it honks as this used to be my prompt to get up and check the
anchor.