I love the spatial organization. I, not even five or six hours ago, had made a note on my iPhone describing something just like it (except where you would get to the spatial organization view by dragging down the bar at the top of the window). My thought was that we (humans) can remember spaces quite well, and certainly much better than we can track a tab's location in an ever-expanding list. IMO, spatial organization should replace bookmarks (and tabs should be treated as bookmarks unless the user has interacted with them since the browser was opened. Maybe I use tabs in a weird way).

Will definitely have to give this a try when it makes its way to other operating systems.