The latest version of Firefox Beta has the following changes:

• Drastically improved memory use
• Added a new rendering backend to speed up Canvas operations on Windows systems
• Bookmark and password changes now sync almost instantly when using Firefox Sync
• Added support for text-overflow: ellipsis
• Added support for the Web Timing specification
• Added an opt-in system for users to send performance data back to Mozilla to improve future versions of Firefox. This can be enabled by installing an add-on
• Fixed several stability issues

Please see the complete list of changes in this version. You may also be interested in the list of changes in the previous version.