Yes, this version brings full IE support.
Hope you like it.
amaznig, thanks, it is a great news.
What IE versions are supported Officially? thx
All other aspects of the theme other than PNG alpha-transparency should work in IE6 as well. If you need to support IE6 and would like to use neptune, you could extend the neptune theme and create all your own icons in gif format. The image extension used in the generated CSS can be easily changed using the global $image-extension sass variable.
For more info on extending neptune to create your own theme see the Theming Guide
Ext JS - Development Team