Personally I just don't get it.
I've experimented around with it but I don't see any advantage to just having multiple applications open and switching from one to another via the task bar, or Task View Button.
If you could save a different desktop layout with different icons etc, then it might serve some purpose but any icon or folder added to any of them appears on all of them.
The only thing that doesn't is running applications.
I pretty much never have more then 4 or 5 applications open at the same time, so I just don't see a use for it.
I can easily manage 5 running programs on one desktop.
It does not have to be used. Certainly, everything can be in one Desktop and hover across the Taskbar or Alt-Tab or there is the new multiple desktop way. Again, it's just to let people know what various approaches to things are available to them. Some may care to take advance of separating things, some may not... no worries.