Over 218 contributors take a part to get ready WordPress 3.0 and they complete there work in half a year.
The Major new features introduce in this release is a brand new WordPress Theme called Twenty Ten, a new API’s for theme developers that allow them to customize post types, taxonomies, backgrounds, menus, headers and short links .
The merger of WordPress and WordPress MU (multi-user) is another major update of this release. So, no need to install a separate installation and you can operate multiple blogs from a single installation.
Another feature of this release is bulk updates so blog admin can upgrade up to 15 plugins at a time with a single click.
For more watch WordPress 3.0 Official Video