A new Unity version (soon to be 5.0) is available for Ubuntu 12.04 Precise Pangolin, but not in the official repositories but the Unity Team PPA. Besides felling a lot smoother and being regression-free (according to Didier Roche), the new Unity testing version also comes with some new features.
In this version, when you launch an application, the menu is initially displayed on the top bar and is only hidden after an amount of time which can be tweaked (along with the fade duration) through CCSM. Until now, the menu would always be hidden and only show up on mouse over, but this behavior made the menu hard to discover for new users, so with this change, the Unity devs hope to make the menu easier to find.
Other new features include: option to change Dash color or add a "Show Desktop" Launcher item and changes to quicklists (Dash icon got quicklists for lenses, etc.)
Here's a video I've created with the latest Unity 5.0 unstable (Ubuntu 12.04 Precise Pangolin) running in VirtualBox:
As for Unity 2D, it finally got buttons for Dash (to maximize or close it):
If you're running Ubuntu 12.04 Precise Pangolin and want to test the latest Unity, add the PPA and run an upgrade.