Is it possible to move all windows from one space to the other?

You can still do this in OS X Lion.

Move to the space you want to move the application's windows to. Right-click on the application icon in your Dock, select Options and enable "This Desktop" in the sub-menu. All of the windows should now move over to the current space.

Out of interest, how do you do this in Snow Leopard?

Edit: At last, I found a way to do this. Open Mission Control, and left-click and drag the application icon under the application windows to a new space at the top of the screen. You can create a new space entirely, or move all of the windows to an existing space. Hope this helps.

You can't at least for now, hope Apple adds more functionality to Mission Control. Although you can move all windows of a particular app between spaces....