The default Unity ("Unity 3D") has a cool workspace switcher that wasn't available in Unity 2D (Qt) until last night's updates. Check out the video below to see it in action:
The Unity2D workspace switcher works a bit differently then in Unity3D (as you can see in the video) and further more, I wasn't able to move a window from one workspace to another from the workspace overview so I had to right click the window titlebar and select "Move to workspace..." to move the windows to different workspaces. These will probably change soon though.
If you're running Unity 2D, the workspace switcher won't work if you use Compiz so to get it to work, run: "metacity --replace".
If you want to install Unity 2D in Ubuntu 10.10 or 11.04, check out this post: How To Install Unity 2D (Qt) In Ubuntu From A PPA. Oh, and if you want to achieve something similar without Unity, you can easily do it with Compiz Expo Plugin and xautomation.
