What’s worth copying isn’t the final product but the attitude. It really is the case that Basecamp is a project management tool that looks and works exactly how 37signals thinks a project management tool should look and work. It is very much unlike any project management software that came before it. They didn’t start with what customers wanted, or with what existing project management software looked like, or by trying to guess what some group of faceless others would want. They designed and built what they themselves wanted, under the assumption that there were some number of other people who would want the same thing.
Oliver