Using Workspaces under Unity
Using Workspaces in Unity is a little different from under Gnome. The functionality is exactly the same, but the mechanism of accessing them is a little different.
Under Unity, you switch workspaces by accessing the "Workspace Switcher" icon from the Unity Launcher:

This will display a grid containing thumbnails of the four available workspaces:

Double-clicking on one of the grid boxes will switch to that workspace:

Note: you can also left-click on a workspace thumbnail, then left-click back on the "Workspace Switcher" icon in the Launcher to jump to that workspace
If you wish to move a window or application from one workspace to another, you can do so (-like you can under Gnome), by right-clicking the window's title bar and choosing one of the various workspace options:

Note: if the window is maximized, you will first need to minimize it and then right click to move to another workspace