I used to run a Taurus fan and it worked quite well. It was very nice having the giant OE fan shroud gone, especially when changing belts, water pumps, etc. I do claim to notice a small power increase and mpg increase. I ran it for for or 5 years.
I had mine on a thermo switch which would turn the fan on at ~210 degrees. I also had a 3 position switch on the dashboard which let me run auto (thermo switch), manually off, and manually on.
I ended up taking it out and putting the OE fan in a few years back though. It was working fine, but with many of my winter trips going as far out into the snow as possible, I wanted to go back to the dumb simplicity of the mechanical fan, as well as taking some load off of the electrical system for winching. I run a 136 amp alternator from a Dodge 5.2L which was more than enough for running the fan, but would get overworked running both the winch and the fan. (As if winching isn't hard enough on an alternator). Perhaps some day I may get crazy and run a very high output alternator, or duals, but for now I am back to the mech. fan.