This release features a lightning fast redesigned linking workflow which makes it easy to link to your existing posts and pages, an admin bar so you’re never more than a click away from your most-used dashboard pages, a streamlined writing interface that hides many of the seldom-used panels by default to create a simpler and less intimidating writing experience for new bloggers (visit Screen Options in the top right to get old panels back), and a refreshed blue admin scheme available for selection under your personal options.
For further details see: http://wordpress.org/news/2011/02/threeone/
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