This is my NC10 desktop :
On bottom, an auto-hide cairo-dock with opened windows, basic launchers, weather, directories, wifi, etc. I configured it to have a good compromise between fluidity and low resource consumption.
On top, an auto-hide gnome panel with systray, ubuntu menu, time, rhythmbox controler and some option which have no reason to be in the bottom dock.
Compiz works only for basic minimize/maximise and open/close effects and there is only one desktop, no more.
They are auto-hidden in order to have all the avaible screen resolution for windows, but hidden gnome-panel always holds 1px on the top of the screen...
Don't hesitate if you have any question !
PS: Sorry if my english is bad !