Restart Firefox is a Firefox add-on that doesn’t even require to be presented: it just restarts your browser to apply changes or complete extensions installations, just by clicking a button. There’s not much to say about it, since it is the simplest extension I have ever seen.
Personas is a Firefox add-on that allows you to change theme without restarting Firefox. After you install it, a little fox appears in the bottom left of your Window. Clicking it will bring up a menu, in which you will see, divided by category and date, all the available themes that you can use.