the dock, quicklaunch and running tasks share the same space, if an app is running it shows a triangle under it, when you hover an icon it gets zoomed smoothli, togather with the icons next to it, and shows the text above the icon of the hovered app.

You can easily make something similar with xlabel for a quicklaunch, but the taskbar icons cant be zoomed in that fashion.

something interesting about the dock: http://www.shell-shocked.org/article.php?id=259