Blogger's new interface debuted in April this year, is now available to users in Blogger in Draft. And, there is no sign up or activation process required; You can simply visit Draft mode, to start exploring the revamped interface!
"Over the last couple of months, we've made significant improvements to our new user interface. We've updated the look and feel of our new design, inspired by Google's newest multi-month design evolutions," a team member of Blogger in draft.
Blogger in Draft is Blogger's equivalent to "Google Labs."
As a Draft users, you get to experience the newest features, including the new design, earlier than other users. If you're not yet on Blogger in Draft, simply go to draft.blogger.com, and check on the "Make Blogger in Draft my default" option on your dashboard.
[Source: Blogger in draft]