I was wondering what use are the workspaces at all, if any. I notice that when I switch to another workspace, all the apps still show in the unity bar and all the icons are still present in the taskbar, and clicking on them takes me to the workspace with those windows. So really, why would I ever care to switch it, and for what purpose? It would have made sense if switching windows completely gave be an empty unity bar where I can start multiple, independent instances of various applications.
Workspaces have been around in Ubuntu well before the switch to Unity. They basically provide you a way to group windows related to similar tasks together, as well as get "additional" screenspace.
The Unity launcher is set to behave so that if you already have windows for an application open, it assumes that by clicking on its icon that you want to return to those open windows, where you may already have tabs or work open. If you want to launch new instances of an application using the icons, just middle-click them.
Workspaces serve this purpose for me: When I'm supposed to be working on homework but have other plans in mind, I keep my homework on the first workspace and my play on the second. Then, when parent comes by, Quick! Ctrl + Alt + Left Arrow! Wow, William, you've made great progress! Keep up the good work! Then I feel guilty and actually do my schoolwork. Thought I should share a specific situation for using workspaces.
Avoiding jumping to Applications of other workspace
Go to New workspace. Now you have Some FireFox Browsers open in Old workspace. If you choose FireFox browser in New workspace, Ubuntu will take you to Old workspace FireFox. Actually you will be taken to Old workspace itself if you select any Application in New workspace that is already in Old workspace.
To avoid this and open any application in New workspace You have to open a Duplicate.
Middle Click the application in New workspace and you will not be taken to old workspace..
You might be able to modify Unity launcher to open a new window of an application whenever an icon is clicked. Try checking out Compizconfig settings manager.
I do agree that if you are a person who launches applications via icons in the bar, there is little meaning in having workspaces.
You may also try launching applications by typing their name after pressing the windows key.