WordPres 2.7 Beta 2  has been released.
Here are the changelog since beta 1:
- The Upload button didn’t always show. Fixed.
- JS on the Dashboard broke for blogs with no comments, causing several UI elements to “freeze”. Fixed.
- Recent Drafts Dashboard module didn’t show correct times. Fixed.
- Various Autosave fixes.
- Redirect after deleting a page from the editor went back to the deleted page. Fixed.
- Fixed loading of translations for default TinyMCE plugins.
- Added avatars to the edit users list.
- Added some missing translations.
- Fixed some validation errors.
- Fixed some PHP warnings and notices.
- Handle inconsistent file permissions during auto upgrade
- Change Publish box layout to better accommodate internationalized text
- Fix quick editing of the last page in the Edit Pages list
- Fix Screen Options for IE
- Fixes for choose tag from tag cloud
- Rewrite rules fixes for certain hosts
- Don’t check for updates on every page load
- Easier post box dropping
- Preview fixes
- RTL fixes
- Fixed broken wp-mail
- Plugin update and install fixes
- First draft of contextual help tab
Download: WordPress 2.7 Beta 2 
You can do the automatic upgrade via WP-Admin -> Tools -> Update.
PS: I would always recommend manually upgrade instead of automatic upgrade as it is more prone to errors.