I just finished implementing BrowserID in an application that I am building. It is quick and easy to use. Perhaps 20 minutes to get it to work. I used OpenID before. OpenID is annoying and difficult. I spent 3 full days working on it.
If only people owned their email addresses then this would be a truly decentralized (eventually) and portable identity system. I do think emails are the best global handle for users that we have currently - we should treat it as such.
The web needs this to be widely adopted. They've got some unique challenges to make it easy to integrate and easy to understand but I think they're on the right track.
At least with email, provided by the email host, the string you get from them will be unique.