Here is a video of KDE's Plasma Active running on a Nexus 7: http://www.youtube.com/watch?v=Bb7isMAmwW0
It is a real use video, there aren't any fancy photos, there isn't any CG in the video in contrast with Canonical's page.
Plasma Active is being actively developed for about 2 years now and KDE 4 was developed from the ground up to be able to adapt to various form factors.
Since most Linux applications run on many different architectures, with such an approach you can keep your low power ARM based tablet and run all your desktop software -albeit a bit or more slower.