Currently turning on fullscreen only affects the current session.

This behavior is by design, since I am concerned that there isn't yet sufficient support for exiting fullscreen in an obvious manner: Users might find themselves stuck in fullscreen mode each time they start.

Some options to manage fullscreen better:

1) Full screen can be started with a command line option, useful for HTPC setups.
2) Use ESC key to leave fullscreen mode. Currently ESC is used to exit a search and is used as a back key, so I'm not excited about this option.
3) Use F11 to toggle fullscreen mode.

Certainly 1) should be supported. 2) and 3) need more discussion/design.

So, initially, a command-line option to startup in fullscreen mode will be supported. That is dependent on bug 10055.