Strobe --
A lot of people find virtual workspaces very useful. Just like a lot of people find a desktop littered with drives and files useful. People think in different ways, and that needs to be respected. There's really no reason to suggest that other people's workflows are somehow improper because they aren't how you work. This is the sort of paternalistic thinking that marred many MS products for a long, long time. We all should have the option to choose how we want to work.
Additionally, most modern virtual workspace managers have little nav panels that show a mini-preview of each desktop so you can see at a glance what windows are open. (fvwm and gnome both have this feature). So not being able to see the apps shouldn't be an issue with the right software.
Further, I must take issue even with the thought that not being able to see an app's window makes it difficult to use effectively. Good god, have you never used the "hide" feature in MacOS? Hidden apps still show up in the process menu or dock, and they're just as easy to switch to. A good virtual workspace manager could just switch to whatever desktop is appropriate when a user clicks the dock icon of an offscreen program. (Though what to do if an app has differnt windows on different virtual displays, I am not sure...)
Zach