Slate Roofing
Modern roofing options are the result of eons of invention and experimentation. Some, such as slate and wood shakes, have remained virtually unchanged for centuries. Others, such as asphalt/fiberglass composites, lightweight concrete, and coated-metal tile, are products of the technological revolution. Each has slightly different durability, appearance, cost, and ease of application.
Tile and slate roofing is very heavy, sometimes requiring structural reinforcement. Slate roofs last much longer than asphalt shingle roofs. Depending on the slate's quality, the roof may last 50 years or more.
Slate does cost a lot more initially, and because it is brittle, may require more repairs over time. There aren't a lot of people skilled in slate repair work, so it can sometimes be a problem to get repairs done.
Among those that opt for slate, most do so because it is perceived to be a higher-end product. Among new homes, you're only likely to see it on the most expensive. If you already have slate, you're usually better off repairing it rather than replacing it.
-- Tips courtesy of HomeAdvisor.com