Before the first login screen came up after a clean install of Ubuntu 11.04 (64 bit) into a new virtual machine in VirtualBox running under Windows 7 (64 bit), a dialog box popped up saying that the hardware was not sufficient to run Unity (paraphrased). All logins have taken me to the Classic DE and I can't find a way to even try Unity.
In the desktop settings, I have selected "Ubuntu" and not "Ubuntu (classic)". The system is configured so I must log in, and a "session" option is available at the bottom of the screen, but regardless of the session I choose, no Unity.
After installing the VirtualBox Guest Additions, the Classic DE would resize as the host window resized, but still Unity would not display.
I don't know if this is a video problem, memory, or something else. The VM has 1024MB ram, 2 processors, 3D acceleration, and 12MB of video memory.
It would be very nice to see what all the Unity fuss is about!