The lack of a good use of space screen has always annoyed me and I think Gnome desktops would all look much better with compact versions of the actual themes. There is no reason for spacing menu items at the levels that are default in Ubuntu.
A compact theme would thus also improve the ergonomy of the interface as one would have to move the mouse less when selecting menu entries, for example. Good work Martin ! Thank you very much.
While I prefer the larger versions for the negative space that they have, I agree that the smaller controls would be very useful on smaller screens.
Doing this makes the windows and dialogues kind of cluttered, though. I think that it might be a good idea to reduce the contrast in the controls slightly (especially dark borders on things like buttons) in order to counteract the jumble.
This might require modifying the engine - I'm not sure how good the various engines are at handling things like variable contrast. I don't believe that clearlooks has anything like a universal contrast setting.
If I had known before that there is a compact theme... I never liked the useless waste of screen space. This was my biggest complain with Gnome. Now, Gnome is really useable.
There are so many ugly themes in ubuntu, so I can't understand the argument that there could be people that would't like a compact theme. It has definitely a useful purpose (The same argument was used for ages about tabs in nautilus. Finally they are there, great!)