Taken from the Mura CMS website:
After months of development and testing, Mura 6 is ready for production use. This release represents a huge leap forward in Mura CMS's user experience; we've created an entirely new UI that greatly improves every aspect of working with Mura CMS. You'll find controls and menus much easier to access and work with, tasks simpler and more direct to complete, and the entire admin experience much more organized and cohesive (not to mention attractive).
Some key features of the new Mura CMS admin include:
Brand New UI (based on Twitter Bootstrap)
Huge improvements in usability
Allows plugin developers to leverage Bootstrap for plugins
Streamlined Editing Forms
Easier access to global and site-specific functionality
In addition to all the new UI goodness, we've added several great new features in Mura CMS 6. Some of the most interesting ones include:
Inline content editing (quick edit mode) - this is incredibly cool!
Image cropping & custom image sizes
Multi-file upload (with drag & drop) directly to Site Manager
Recurring Events in the Mura CMS Calendar
Improved and updated MuraPlayer plugin (formerly MuraMediaPlayer)
Updated Locale Translation Manager plugin with new "export for translation" functionality that allows the export of content to be sent to translation services for importing after being translated.
Theme-based site configuration via XML
The WYSIWYG editor has been upgraded to the newly released, CK Editor 4
Updated MuraBootstrap theme and site bundle
MuraBootstrap carousel plugin
Full Details here: http://www.getmura.com/blog/mura-cms-6-now-available/