For RC version, the first of 3 other expected until final release of WordPress 3.5, the December 5 (right there, there is nothing), few changes are visible from the latest betas except final welcome screen, where lists all the most important developments, namely:
- New charger and image management.
- Several galleries can reorder with "drag and drop" images of each other.
- Attached Image Editor.
- Icons planes in the visual editor.
- Square buttons instead of round (presumably more modern).
- New Default Theme Twenty Twelve (Twenty Ten is no longer in the official distribution but can be downloaded separately).
- Desktop HiDPI for a better experience with retina screens .
- The whole area is now adaptive management to the device that is being displayed.
- Improved support elements "embeddable" with oEmbed (Instagram, Slideshare, Soundcloud).
- Plugins favorites .
- Improvements to multisite.
- Link management disappears .
- XML-RPC enabled by default (sic).
- Updated APIs (TinyMCE, jQuery, jQuery UI, jCrop and SimplePie).
If you plan to update your site seen preparing evidence and updated to keep trying and other plugins .