I think I posted in the old thread.. but I'll share my experience again. I put a metal roof on our renovation last year, and the cost was nearly a wash with what shingles would've cost us. Material cost was about $2k (13 square roof on ~1000 sq. ft. house). I'm going to put another metal roof on my old house in a couple of months (trying to get it ready to be a rental or sell), and I'll post the costs and my experience when I do it as well.
The house across the street from my old house was foreclosed on last year and some renovators bought it, fixed it up, and flipped it. They did quite a bit of work and the finishing touch was a nice looking green metal roof. They put it on top of the existing ratty shingle roof, which I personally would not have done, but it looks beautiful. They bought the house for $69k, sold it for $130k, and the new owners told me that the roof was a primary selling point for them ("it's a lifetime roof!" the wife said..).