The Preview Themes plugin allows wordpress users to preview all installed themes without having to activate and deactivate them simultaneously.An updated version is likely to come up soon as this is the initial development release.
Note:The docs will be available at http://dreamsdeveloped.com pretty soon.
- What does the option to show the Preview Themes Toolbar do?
It provides a simple scolling toolbar on the preview screen allowing you to preview themes swiftly in the preview window itself.
An upgraded version is on its way.