I'd like some input from homeowners who have metal roofs?

We are thinking about having one installed. I hear they help quite a bit in conserving energy, especially in the summer. I was wondering if anyone out there who has a metal roof on their home has noticed a difference in their bill much, and is there much difference in the way the house itself feels? We have a 1.5 story home, the bedrooms are upstairs and during the daytime the AC could run all day and still wouldn't do any good. I realize insulation is a big factor in this of course but wondering how much if any metal roofs help, thanks :)