If you don't have an OpenGL based video card ( no ARM machine does, they all use a subset of OpenGL called OpenGL ES ) then upon logging in, you get a long dialog explaining that you need to logout and choose classic desktop. And it has an exit button. When you click said exit button, after a bit it loads the classic desktop, however the xsettings manager doesn't get started (or it might, just depends on if it feels like running it seems) and gnome becomes very ugly.
There is no mention of Unity-2D which is a version that is QT based. And it suffers from the same issues, xsettings may or may not launch and then you have a ton of dialogs about apps crashing in the background ( this is with either Gnome "classic" or with Unity-2D ).
Ubuntu made great strides in making the Linux desktop accessible for everyone, but this latest release shows just how much further they need to go.
Keep in mind that at the time the decision to write and use Unity was made, the Gnome 3 desktop was in an absolute mess. A lot of work has happened since then and it would be even better if Mark Shuttleworth could swallow his pride and just scrap the Unity project and work with upstream like before.
I mention the ARM bit at the beginning of my statement if only out of frustration due to the fact that our company provided Ubuntu developers with over 50 machines that are in either a desktop configuration or netbook yet it still doesn't run anywhere close to where it should on them.