The traditional Gnome desktop wasn't that polished. Panel was a disaster, because everything was positioned absolutely, instead of "this is to the left/right of this, here's the large space separating the left and right halves" all of your little "applets" would end up rearranged if you changed resolution.

So a good way to do it would be:

    [Menu][Launcher]========(horizontal fill)=======[Tray thingy][Clock]

Or for the default bottom bar:

     [Taskbar =========== (fill horizontally checked)][Workspaces]

So everything can reflow regardless of resolution. This is basically how toolbars in Cocoa work, for what it's worth. Both shell and Unity fix this problem in different ways, but it's definitely an improvement for everyone that uses a projector occasionally.