Weirdly enough I'm the other way around. I have an android 2.3 device and find the UI frustrating. A mobile version of Unity with different lenses and searches would be far better, though I would want access to android apps.
I would find this useful assuming I could connect a keyboard and mouse to it. Assuming Android and Ubuntu could be dual booted quickly enough and I had a decent stand for tablet I could forgo a laptop entirely.
Ubuntu is great for doing computery things, like coding, or setting up servers etc. On a tablet, I'm not coding (too fiddly to type $[]@% etc), and not using it as a server, but I am using it as a map, as a book, as an email machine etc.
To be honest, I'd rather run Android on a laptop, rather than Ubuntu on a tablet.