This feature is widespread in the professional sites selling themes, making this a download plugin must for many.
* Compatible with WordPress 2.8.3
* Tested on 2.7.1 and WP 2.8 to 2.8.3
* Preview any existing theme without activating it.
* Allows you to add different CSS styles (more than one) in the same theme.
* You can customize the look & feel and layout (using CSS).
* Hides the private themes!
* You can display the amount of previews (popularity).
* Preview persistent (automatically updates all links to show the same theme even if you change the section, etc.).
* Lets you include info about this theme and can also be downloaded directly from the bar.
* Many more options available …