You can place several object on a layer and hide or move them as a group. The menu of www.riverclack.nl is partly made with layers. The bottom 2 buttons are placed on layers to move them up and down.
I use layers often in my design for page headers & footers. Though I find layers cannot be resized dynamically relative to the page size like in other software I use. When ever I try to input the width as 100% in the 'custom html' it doesn't seem to work.
I would really love to see this feature added soon.