Macworld UK discusses Leopard's Spaces feature.
Expose will be closely integrated with Spaces. This means that you will be able to see all windows in all spaces using Expose, offering a quick and easy way to locate and switch to specific windows among multiple Spaces.This may not be obvious at first, but the way Apple chose to implement Spaces pretty much gets in the way of Exposé. If you have created several Spaces and activate Exposé, it will only minimize windows in the current Space. Windows in other Spaces won't be visible.
If you want to see all your windows in all your Spaces, you need to reveal all your Spaces first (by pressing F8), and then use Exposé, which will work in the minimized Spaces: each window will be scaled to fit the minimized representation of its Space. Currently, before Spaces, all your windows would be minimized to fit the entire screen. That will no longer be the case when you have Spaces. If a Space has too many windows, Exposé will make them miniscule, while windows dwelling in other, less crowded Spaces will be scaled to large enough sizes.
If you have problems picturing it all, this Google video I found should help.
I would certainly prefer a solution where all my windows in all my Spaces would be scaled down and distributed to fit on the full screen. First, it would be a much better use of screen space. Second, for me, Exposé is all about revealing everything (as implied by its name). If I hit F9, I do that because I don't want to worry about switching apps or moving windows out of sight: I want to see everything. And no, I don't want to worry about Spaces either when I hit F9. And third, I don't want to use two consecutive keystrokes instead of one.
I think Spaces basically breaks Exposé in their current implementation. I'm not saying that the current solution is without merit, several users may actually prefer it to the alternative that I miss. But I don't see any reason why Apple couldn't implement that one as well. I certainly think we need a way to let Exposé minimize all windows on one screen, ignoring Spaces.
If you have any information suggesting that such functionality is available or is being planned, please let me know.