it will slow all your accessories pulleys down. that includes your alternator, water pump, AC comprressor, and PS pump. I haven't noticed any difference with the slowing down of these items. but, if you have a big stereo system or something, your alternator may not put out enough juice to power everything. especially at night when you run the lights!
I have noticed the AC isn't as cold when city driving, but it doesn't really bother me.
And there is no effect on the power steering.
in essesence, your crank pulley is 1 inch smaller and your water pump pulley is 1 inch larger. when I installed my Steeda UDP's I was afraid my car would run hotter. but this hasn't been the case at all.
2005 Mustang GT M5
-I reject your reality and substitute my own-