I suppose you could use something like VNC or Remote Desktop. What would be really nice would be if you could leave the notebook running on the table, plugged in, and just take the screen with you. You couldn't watch movies that way, but you could easily run Photoshop or other CPU-hogs, and surfing would be much snappier than rendering with a smartphone processor.
There must be some kind of connection between the two parts, anyway, to copy files back and forth between them.
there's some link since it knows to switch OS, though thats probably just flicking the input for the screen, win7 is probably running away on the keyboard half all the time in hibernate mode and they've optimised it to wake quickly
for people running processor intensive stuff it would be superb, the use you suggest would appeal to a lot of people as they'd not have to buy two laptops but could use one instead, start photoshop doing a job, unplug the screen, maybe set growl to tell you the job is done etc, actually it would be nice if they integrated something like growl into it so you could at least get notifications of what's going on on the other part of your machine
i suspect you're going to have to open all your apps when you dock it or separate it each time, you can probably leave them running if it goes to sleep and then reactivate them when you wake the part you're using, all it would take is for them to work something into the code to wake up the apps that don't do it themselves