One weird thing I noticed when I upgraded to Firefox 4 is that you no longer get offered the option of saving your tabs on exit.
This often came in handy for me at times when I needed to restart the browser for what ever reason (plug-in install, computer restart, etc) so I do wonder why it is disabled by default on Firefox 4.
Perhaps it is not used as often as I thought it might be…
Anyway, you can easily re-enable this prompt by following the simple steps below: