I think time has determined this to be a 'relatively' safe mod. If there's a problem to begin with, then the pulley will amplify it. If everything is in spec, life should be fine. A lot of people have put 30k+ on their cars now with the pulley.. no problems.
I wouldn't sweat it.. just do it!
Later
My oldest sig circa 3/97: Ever notice the Mustang pony runs the wrong way on the front of the car?