I don't have experience with the 4.7, but I had one on my Tacoma for less than 24 hours. The damn thing made so much noise, and the amount of draw it put on my alternator made it unbearable. I noticed absolutely no increase in power, and I was supercharged. The only reason I would see someone using one of these fans is if you were strickly rock crawling or mudding, where:
1. The truck does not move more than 5mph but the RPM's can be high for a long period of time (mudding)
2. You don't mind the vibration of the fan shaking the living hell out of the truck. (fans may have not have been balanced properly)