Things to look forward to in the new interface:
- An action bar that uses icons instead of text labels
- A completely new interface for conversations
- Profile pictures next to contacts
- A flexible layout that adapts to any window size (will be useful when viewing on smartphones and tablets
- Display density options like in Google Docs
- Re-sizable chat/labels sections
- New high-definition themes
- An updated search box that includes advanced options.
The video was unintentionally made public and has now been taken down but a mirror copy exists (linked to above). Screenshots can be seen at “Google Operating System- Unofficial News and Tips About Google”
More information about the new interface can be found on Google’s Official Gmail Blog