According to http://askubuntu.com/questions/88031/how-to-resize-the-top-panel-in-unity, the top panel height is hard coded in Unity's source.
I propose that the panel height be, at least, proportional to the font used if not configurable by hand outright. I prefer slightly larger font sizes which make it look cramped. Also, the text size settings in Universal Access should have an effect on it too.
Maybe scale the indicators/icons as well?