New features:

• Twenty Thirteen Theme: A responsive theme that is now the default for new sites. The Twenty Ten, Twenty Eleven, and Twenty Twelve (along with the 100+ other themes we have installed) are still available for use.
• Local Autosave: Your edits are now saved locally in your browser in addition to on the server so if you lose network connectivity while editing you won’t accidentally lose your work.
• Post Locking: When you’re editing a post and someone else starts editing it there is now an interface letting you know that someone is taking over editing. Also, your autosaves are unique to you, so other editors won’t overwrite them.
• Easy Audio/Video Embeds: Paste the URL of a .mp4 or .mp3 file into your post and WordPress will provide the player.
• Revision Browser: The interface for looking at post revisions is significantly easier to use.