UPDATE! (13 Feb 2008) I am not updating the script source here any longer -- if you install from here, your pages may not display correctly. The latest script can be found here, on my personal site.

The new StumbleUpon beta layout adds a sidebar with lots of buttons, tag clouds, and other elements that can be distracting when viewing a stumbler's content. This script provides a much cleaner layout for the SU beta by hiding the sidebar on most pages, toggling the sidebar on and off via the "Sidebar" tab in the top tab bar, and moving the Inbox and Recent Visitors icons into the top tab bar. Note that the sidebar is not automatically hidden on the "What's New" page, because it contains the last 10 visitors to your site.

Notes: This script has been successfully installed and run on machines with Windows XP Professional, Windows XP Home, Windows Vista, Linux, and Mac OSX with the latest Firefox and Greasemonkey versions installed.

I have not yet hidden the sidebar on the Websites, People, Videos or Review pages.

If you have any problems or questions about the script, please message me at SU.