Farhad Manjoo of Slate asks whether it's worth it, which aligns pretty well with my thinking. ".com" is the entrenched default, and the new TLDs we've seen so far simply haven't had a great deal of success. I very much doubt that the ability to register "transformers.movie" will substitute for "transformers.com" and "transformersmovie.com". The ability of well-known Internet brands to shorten their URLs (.ebay or .facebook) seems marginal as well--- those brands are already easy to find.
I wrote in 2002:
For example, if there was a .consulting top-level domain, then Andersen Consulting might want to register andersen.consulting. But if andersen-consulting.com is available, this is no harder to remember and equally distinctive. Further, Andersen Consulting would not want to own andersen.consulting if another party owns andersen-consulting.com, given that many customers would try the .com version first, or confuse the two names.
Similarly, the large base of existing registrations effectively discourages users from learning to try new domains. For example, the San Francisco Museum of Modern Art owns both sfmoma.com and sfmoma.org, but not a .museum domain.[***] Users will have more luck trying to find organizations in existing domains than learning new ones, for the foreseeable future-- especially if the number of new TLDs is large, creating additional confusion about the appropriate category.
Any potential new top-level domain is thus insufficiently distinguished from the hyphenated form to truly offer a distinctive name. Nor will a business which cannot get the short form of its name in .com be as satisfied with a short form in a different TLD, since customers will have to remember which TLD instead of relying upon the default.
[***] As of 2009, this is no longer true. The Minneapolis Institute of Arts has artsmia.org (which I never would have guessed) and also the corresponding .com, but not .museum.
If I were an economist instead of a networking geek, I might rephrase this as domain names being complements rather than substitutes.