Keyboard-focus has a nice selection highlight, which can be used for other purposes like mouse hover. They're very similar anyway. However, keyboard-focus could also use the tooltip that tells the user the name of the app he's currently focusing on. Maybe, both hover and keyboard-focus can use the combination of highlight and tooltip.
There are also missing button states like when an app icon is clicked and when doing "Scale" for one app. On OS X, clicking an app icon on the dock will make the icon dark and "Scale" for one app will make all other app icons dark. We don't have to do it the way OS X does it, but there should be visual representations of these states.
It could be too late for Natty, but it would be nice if some button states can have the right feedback in time for 11.04.