Here is the video showing Ubuntu 13.04 Raring Ringtail (still in development at this time of writing) running on Nexus 7, a 7.81″ tablet which runs Android Jelly Bean by default.
It is expected that more announcement will be made regarding Ubuntu tablet at the upcoming Ubuntu Developer Summit (UDS) in Denmark, which Mark Shuttleworth himself drop a hint that future Ubuntu development will focused on mobile platform. He even encouraged attendees to bring Nexus 7 to the summit.
Its refreshing to see Ubuntu can be ported on tablets. It open up several opportunities to integrate Ubuntu operating system with mobile platform and together with the possibility of cloud computing, it will be able to unify the way people use their computers in their daily life. However, a new GUI has to be designed in order to make Ubuntu usable and convenient to be used on tablets.
All in all, it is a bold move from Canonical.