More details in this blog post:
http://www.bring2mind.net...ge-6-1-Released.aspx

This is the change list:
Change: Dependency now on DotNetNuke 6.0.0
New Feature: New search UI allows you to see the advanced search options and put DMX on a page for searching purposes (DMX-474)
New Feature: Added the ability to add a folder provider to DNN (DMX-475)
New Feature: You can opt to use a jQuery component (PageGuide) to show all help texts in DMX
New Feature: New API class to gather methods that are often requested by others
Enhancement: Storage provider supports the notion of direct link. This allows a storage provider to provide direct access to a file.
Enhancement: S3 storage provider now supports direct access to files, bypassing the web server. Security is maintained using S3's ability to ask for a temporary key.
Enhancement: New default template based on Bootstrap css framework
Enhancement: New IFilter logic in the Lucene search provider to help with content indexing issues
Enhancement: Added setting to specify sender email address for notifications (DMX-468)
Enhancement: You can now choose how DMX handles permissions upon move: keep old or assume from destination folder
Enhancement: WebDAV cookie timeout now configurable
Enhancement: Revision of how module settings are rendered to improve usability. Settings specific to a UI are now grouped and loaded dynamically.
Enhancement: You can now specify which admin menu you'd like to use just like the main menu (Ajax UI only) (DMX-473)
Enhancement: Ensures Word loads document in front of browser when opening through WebDAV
Enhancement: Root Pattern now supports "group" object for DNN 6.2+ allowing group based folders
Fix: DNN Social groups now also show up in the permission grid.
Fix: Renaming of css sprite classes to prevent clashes with other css frameworks
Fix: Synchronization logic now adapted to cater for long file names
Fix: More defensive coding around logging to prevent module writing to C:\DMX when not in http context (DMX-465)
Fix: Fix in data layer to account for unauthenticated users role (DMX-471)
Fix: Several enhancements in SQL to improve performance and uniformity
Fix: Exception made for permissions maintenance (pruning of deleted users). It now only works on data of portals that are not part of a site group (DNN EE feature)
Fix: Various enhancements to search logic
Fix: New method for storing content in Lucene to fix issue where the stemmers were not storing content correctly. It is now stored both using tokenized analysis and using the Snowball stemmer. (DMX-476)
Fix: Admin VIEW/EDIT/ADD permissions checkboxes now disabled (DMX-464)
Fix: Ensure download method is type default when downloading
Fix: Fix to WebDAV wildcard handler


As usual: backup your installation before upgrading! Better safe than sorry.