I discovered that using the settings menu from the main top bar had the button compiz to click. I did so - and alas - all of a sudden the desktop pager and all buttons are there - still the bar being invisible - the way I wanted it. SO it sems that this has to be enabled to make the invisible option working correctly.
Never tried it that way. Glad you got it working. I should point out that the setting you're referring to is e17 compositing, which is not to be confused with compiz. If you enable compiz, e17 will not start.