Raring has had a number of improvements in this area which should improve the workflow for someone using multiple workspaces.
Lets look at some examples:
In this example you can see that I have Firefox and Terminal open in different workspaces - with firefox open in two instances on separate workspaces:
Look closely at the Launcher:
Firefox is shown with a full pip - thats the arrow shown. It only shows one since this is the only one running in this workspace.
The terminal pip is a narrow version indicating that its running in a different workspace. Thus you get an instant indication of BOTH applications running in the workspace as well as possible other applications running.
If you had two instances of firefox running in the workspace you would have two pips.
To create another instance of Firefox on another workspace, right-click and choose one of the first two options shown:
To flip between different instances, choose from the window title shown in the right-click quicklist.