Concierge.com's insider take:

If you can forgive the rather humdrum name and slightly away-from-center location (trendy Nişantaşı, about a five-minute cab ride from Taksim Square), you'll be treated to a modern boutique hotel of European-caliber quality and design. Opened in 2006, the Sofa shot straight into high demand, and advance bookings are advised to secure one of the 82 rooms. Standard doubles are spacious and decked out in an agreeable, if familiar, contemporary style, with bathrooms tiled in glass and dark marble. Some have views out onto the streets below; inner rooms face a gurgling Zen garden at the bottom of a large light shaft. The psychedelic elevators will thrill the easily amused on the way down to the reception level, which shares space with a serious restaurant and a casual café. The serene Taylife spa on the basement level offers a profusion of treatments, plus high-tech machines that might be more at home at space camp. Service is well-meaning, if a bit wanting in English language skills. The obvious model here is W Hotels—down to the "request anything" button on the telephone. Now that the American chain has opened its own outpost a few blocks away, however, the Sofa will likely need a bit of reupholstering to remain competitive.