Oneiric: The Dreamy
Unity Panel: Indicators
The indicators and their menus are cleaner and better organized than in any other previous version of Ubuntu. While it's a small change, logically grouped and labeled menus cut down on the learning curve.
Unity Launcher: Icons
Launcher icons can now display information about the application. Examples include the Software Update icon showing the number of available updates, and the Thunderbird icon showing the number of unread emails in your inbox.
Dynamic icons are also not confined to the Launcher. When installing applications in the Ubuntu Software Center, a Progress button appears in the toolbar. This button shows how many applications are currently being installed, and the icon rotates when installations are in progress.
The inability to move back and forth between Dash screens was one of our biggest complaints about the Natty Narwhal Dash. Luckily, backwards navigation is now possible in the Oneiric Ocelot Dash. The integration of Lenses into Dash also helps to clean up the Launcher.
Ubuntu Software Center
The new focus on popular applications (FOSS or otherwise) is a step in the right direction for Ubuntu. While long-time Linux users and free software advocates may scoff at the appearance of proprietary commercial software, the goal of this distribution is mainstream end-user adoption, and the masses flock to the platform offering the titles they want.
Ubuntu One is a fantastic cloud storage service, whether you use Ubuntu or not. If you're going to use Ubuntu you would be nuts to not take advantage of Ubuntu One.
Sometimes it's the small stuff that makes a difference. In Ubuntu 11.10, there are many little details that serve to enhance the Unity experience that launched in Ubuntu 11.04.
The transparency of Dash, and obfuscation of anything behind it are a plus for the overall look of Unity.
Another little tweak that has gone mostly unnoticed is the addition of a camera shutter sound and flash when taking a screenshot, much like on a smartphone.