First Unity was developed for Netbooks. But the Netbook Market is shrinking. Unity is not specialized for tablet pcs like Android 3, but it may work well with some specialized Apps for those devices.
Unity is still nice for Notebooks with small displays, but there is no big advantage on the desktop compared with other desktop environments like Gnome 2/3 or KDE.
So what's the point?
My first suggenstion was a hybrid between tablet pc and a desktop, for example for a manager. He can plug the tablet in a docking station in his office and he can work at a normal desktop, whats not possible with iOS or Android.
If he is in a meeting he can use it as a tablet to make notes, for example. Or if he is somewhere else outside the office or the company.
Same for normal users. They can dock the tablet and use it like a normal desktop pc or they can lie on the couch and browse in the web, read a book or chat with friend.
So, thats my suggestion. But what is the real plan for Unity or Ubuntu in general? I'm curious ;)