Files and programs can be either visible on all work spaces or only
visible on one workspace. In terms of working with multiple programs
and files then having them only visible on the one work space is the
most convenient but sometimes it's useful to have something visible on
all work spaces ( i.e. a text file for copy / paste operations between
multiple open files ). In general, it's less confusing to have a file
or program only visible on the work space it was launched in.

Not had much success getting work spaces working as I'd like in Unity
and tried the 11.10 Beta 2 in VBox but although it installed and ran
OK the graphics quickly screwed up big time - going to give it another
go with the 32bit version to see if that works any better. 11.04 in
VBox doesn't allow Unity