One of the true pleasures of Key West is the drive down there, as it's a long and beautiful journey hopping from island to island across scenic bridges. But even if you fly in this is a worthwhile destination.
There's no doubt that it's touristy, but with its remoteness is also has something of a small-town feel that you don't get in most other tourist meccas. There aren't a lot of good beaches, but there are excellent views everywhere, and the sunset ritual at Mallory Square is a highlight for nearly every visitor.