A good concealed fastener, standing seam metal roof looks great and is just about the finest roof you can buy. It will last 50-75 years or more without issue, maybe longer. However, you will pay probably three times more than you would for a shingle roof, so you either need to plan on staying there a long time to justify the cost, or just like the look and be willing to pay for it. It will probably improve the resale value some. It could reduce insurance costs in potential fire areas, ask your insurer.
As some have mentioned, the devil is in the details. You need good sheet metal craftsmen doing the work to get all of the flashing and penetration details right or it will leak like any other roof. If these are done correctly, you will never have a problem. Metal roofs are tougher than shingles, so I wouldn't worry about hail, if you get damaging hail, that's an insurance claim. Like any roof, it's always best to minimize the penetrations and keep any unnecessary junk (like satellite dishes and solar panels) off the roof altogether. A steep metal roof can be dangerous to walk on if you ever need to get up there to clean leaves or sticks.
The majority of metal roofs you see are not "concealed fastener, standing seam, metal roofs", they are cheap, thru fastened, ribbed, painted, pole building siding / roofing. Many of these you see get installed right over the old shingle roofs on furring strips which is a bad idea. The old shingle roof should be stripped down to the deck, new underlayment installed, then new metal should go right down on the deck. Deck also needs to be thick enough and of the right material so screws will hold.
Color fade isn't much of an issue on the good metal products if you buy something with a high quality Kynar painted finish. In my opinion, plain unfinished galvalume (silver) looks pretty nice too and it's a bit cheaper than painted and will last equally as long.
