In a supporting app it autosaves all state, which is quite a bit more than just "re-opening documents". The ideal Apple is working towards is making the running state of an application irrelevant. They'll probably never get there entirely, but we've seen that it can work in practice on iOS. The friction for quitting is certainly decreasing by leaps and bounds.
Spaces was a failed experiment, at least in Apple's eyes. At this point it would be wise to either find a 3rd-party replacement or embrace Mission Control Spaces, otherwise you'll just be stuck in time with everything else slowly growing obsolete on you.
Is there anything that runs on Lion and has similar capabilities to Spaces? Right now I have 9 spaces and each is at most 2 switches away from all of the others. My impression is that if I install Lion and set up 9 spaces, the outermost ones will be 8 switches apart from each other.
I'm not sure, but if not now I'm sure there will be soon.
For quick navigation of 9 spaces with assigned apps it's probably best to just use Ctrl-1 thru 9. Spacial navigation is pretty much dead between full screen apps and auto-rearranging of the spaces (well, you can turn that off I guess), so I decided to embrace Apple's new idea and see how it works.
It's a huge change from Spaces, but for me (using 4-6 SL Spaces) never reached a level of perfection due to the small bugs and unpredictabilities in the system. I'm going to give Apple the benefit of the doubt and see if they can come up with something better. So far there are some real nice touches to Lion window and space management.