[Porsche-O-Phile]

Agreed about copper. Beautiful and durable, but also extremely expensive and looks very out-of-place on all but stone neo-gothic type buildings.

Standing seam systems are very, very good. They can last many years without requring any sort of maintenance. However one issue I do see with them is that the openings need to be properly detailed for penetrations. Bathroom vents, exhaust fans, skylights, chimneys, etc. need to be properly flashed, counterflashed and sealed and have crickets provided where appropriate. This is quite often forgotten and your local handyman residential roofer won't have a clue how to do this properly, so you'll either end up with a leaky roof (bad) or a clean, nice looking metal roof with huge gobs of sealant glop around every opening that looks like hell. You NEED to use a roofing contractor that installs these systems a lot (find guys that do commercial buildings - they probably wouldn't turn the work away these days). And make sure the manufacturer provides flashing details and the penetrations are constructed accordingly.

If everything is done right by a skilled, familiar roofing contractor, a standing seam roof should last 50 years with no leaks.