Almost no hp gain. One guy from another forum actually reported a torque loss.
Read through the last 2 months of posts here and see how many E fan problems people have, it's alot. Works better on newer cars because the computer controls the fan, not an aftermarket fan controllers.
Spend the money elsewhere.
Only time i think it helps is to get the a/c to work better at idle.
For a hp gain estimate, consider it this way, removing the entire belt gains somewhere in the vicinity of 25rwhp, that's no PS, no water pump, no alternator, and no fan.
You'll just be removing the fan, you still have to turn the water pump.