Google has essentially mastered the release process for it's Chrome Browser and made version numbers for their software essentially obsolete. The release often strategy is an excellent approach to client software. It's good to see Mozilla following the same path.
Think of any major website, even the fancy Web 2.HTML5 ones... do they have version numbers? We took the same approach to our client software as an online web service. That is... we treat releases as a means of getting features out to users and not goals in and of themselves. It's about flow