Update to version 3.3.

Highlights:

* Easier Uploading
    - File Type Detection - A single upload button
    - Drag-and-Drop Media Uploader
* Dashboard Design
    - New Toolbar in the dashboard, combining the Admin Bar and admin
      header
    - Responsive design for some screens, including iPad/tablet
      support
    - Flyout menus, providing single-click access to any screen
* New User Experience
    - New feature pointers, helping users navigate new features
    - Post-update About screen
    - Dashboard welcome area for new installs
* Content Tools
    - Better co-editing that releases post locks immediately
    - Don't lose widgets when switching themes
    - Tumblr Importer
* Under the Hood improvements
    - Use the postname permalink structure without a performance
      penalty
    - Improved Editor API
    - is_main_query() function and WP_Query method
    - Remove a number of funky characters from post slugs
    - jQuery 1.7.1 and jQuery UI 1.8.16
    - A new Screen API for adding help documentation and adapting to
      screen contexts
    - Improved metadata API
* Performance improvements and hundreds of bug fixes

More changes at http://codex.wordpress.org/Version_3.3

(morr)