A new, very stylish hotel called Citizen M just opened near the airport. A friend of mine stayed there recently--rooms are prefab pods, but the furnishings are great, real-deal design icons (Eames, etc.).

It's true, Schiphol is very close to the city. If you are open to the idea of coming to the city, look for hotels near the RAI convention center and train station. The train from Schiphol to Amsterdam RAI takes just nine minutes--you'll see lots of KLM staff taking this sneaky back route. Hotel selection around here is cheaper and nicer than anything walking distance from Centraal.