One of the things people don't notice about Windows is that (I don't understand the exact circumstances) applications can disconnect from a running GUI session and then reconnect without needed to be restarted.
The biggest example that I can think of this happening is one of the reasons how Microsoft was to enable much greater (perceived) stability for graphics drivers for Vista and Windows 7. Many Windows users can testify that occasionally when launching a 3D game or some app or something the entire screen will go black and then restart up again. What has happened (from what it seems like anyways) is that the kernel caught a exception or some other problem with the graphics drivers and had reset everything. The GUI is rebuilt and then all the applications still running are loaded back up and reconnected to the GUI session like nothing happened.
With Wayland, and it's compositing-based windowing system, seems like this sort of thing should be possible.