With the new technology of composite deck boards, and even a specialized "oven" made by Trex (see below) for bending these boards, curved decks are all the rage.
However, the equipment is expensive, and the process is labor intensive. This means curved decks aren't cheap. We at ProDeck can curve decking, if your budget allows, but we have begun practicing a much cheaper method that will give your deck an actual curved shape, without actually having to curve the boards.
These two images are of a Trex display deck we built for Dixieline Lumber in Kearny Mesa. By running the direction of the decking perpendicular to the edge of the deck, you can achieve a curve simply by gradually increasing the angle of the cuts on the board ends. The thin Trex fascia bends easily around the curve and creates a clean, finished look.