Question: I'd like to run the new Unity interface from Ubuntu 10.10 inside of a VirtualBox VM (host is Ubuntu 10.04). Is that possible? Thanks!

Answer: 
So, to answer the title of this article:

"How to create a Ubuntu Netbook 10.10 Unity VM under VirtualBox"

You can't. The Unity interface can't run in a VirtualBox guest. You can, however, use the default gnome shell common to the regular Ubuntu distribution -- but that is not trying out UNR...
With VirtualBox 4.0 it is now possible to test Unity under Ubuntu *11.04*.  

The 5-steps howto is [here](http://www.webupd8.org/2010/12/how-to-test-ubuntu-1104-with-unity-in.html).

I did not tried to run Unity under 10.10 in a VM but if you still want to, you should be more lucky with the latest VirtualBox release.