theme-selector

Theme selector enables users to preview and activate themes through an interface similar to tumblr.
A new button is available on the admin bar and it works as a shortcut to this new theme selector interface.

If you want to test and change themes from your WordPress Site frontend this plugin is for you.
For the ones using since 3.3 Tumblr Importer this is one way to perform theme selection as you know it.

Feel free to give us some feedback.