When you Install the Unity Desktop Beta onto a Ubuntu 10.04 Netbook Edition system it Installs side by side with the default Moblin Desktop and you select which one that you want to login to on the login screen, The 10.04 Netbook Desktop is the default one though.
Once the Unity Desktop is loaded up it looks similar to the default Netbook Desktop with the Panel on the top of the screen showing the Left to Right: Ubuntu Menu, Network Manager, Battery Indicator, Sound preference, Mail and Broadcast Message, Time, Social Networking Menu and Session Menu.
When you click on the Ubuntu Menu you now get a drop down menu with Search feature instead of the show Desktop action in the old Desktop.
The Side Bar/Desktop has been cleaned up significantly since 10.04. Instead of having a tabbed Desktop you have a sliding side bar that houses your favourite programs, Trash can and quick access to the Programs and Files and folders. There is also access to a Mac OSX feature that shows all your open windows as thumbnails.
As this is only a Beta version of the Unity Desktop and running on top of Ubuntu 10.04LTS Lucid Lynx and no 10.10 Maverick Meerkat it doesn't have all the updates that 10.10 will contain. If I can get hold of a disk Image of the Pre Release version of 10.10 Netbook Edition I'll download it and give it a try. In the meantime here is a rundown of all the new features of the different Editions of Ubuntu 10.10.
For more on the Unity Desktop please visit this Blog.