Meh, to all haters: u r funny! What difference does it make if Spaces is not 100% totally brand new never seen feature, or something that's been copied from somewhere or done differently somewhere else? What matters is how useful is Spaces going to be to the end user? I have a sneaking suspicion that Spaces will be way more polished than MSFT's powertoy, or some virtual desktop manager from linux or some hacked up solution from somewhere else. Yes, those other solutions exist, but I'm not using them because they are not as well polished up and thought out - implementation is often more important than the basic idea... that was the trouble with early Linux solutions - sure, you couid do X, Y or Z, but you had to do it in a really hard or roundabout or unintuitive and basically geeky way. Apple would take the same idea, and make it USEABLE. I'm not saying with everything (boo spotlight!), but often. That's what I'm counting on with Spaces.
The basic idea behind Spaces is valid - I don't care who invented it, but I do care that Apple finally implements it in a user-friendly way. Personally, I see a lot of use for it in my workflow. Often I'm multitasking on totally different things, and it would be great to have superfast ways of switching to collections of apps devoted to a specific task. I dig it. I'm sure it's been hacked together somewhere, but I bet Apple will make it actually useable.