Another dictionary that meets my criteria for actually buying one: recently updated, lots of usage examples. This one also has a nice reference section, with interesting items such as: biological classification, a style guide, proofreading marks, major divisions of geological time (a good mix of sections you would and wouldn't expect from a dictionary).
I'm unlikely to buy another hard-copy dictionary since the information is so easily accessible on the internet, but it's nice to be able to page through a reasonably heavy tome and discover new information.