I just survived my first Firefox Reset and lived to tell about it.

I was experiencing some weird cross-site stuff for one of work's web tools, and decided to give Firefox's Reset a try. It actually worked!

My concern was that, because it deletes all your add-ons and customisations, I would lose them. Fortunately, I also use Firefox Sync already. So that meant, after Firfox had cleaned itself up, it re-downloaded all my custom goodness and re-installed it.

One caveat: you do have to Restart Firefox after Sync has done it's bit to re-install Addons. After that, everything is as it should be. Hurray.

The steps to Refresh Firefox are:

Go to about:support
Press the Refresh button in the top right
Wait for Sync to finish (you can check how it's going by looking in about:addons to see if your Extensions are all there yet)
Restart Firefox (either from the addons page, or by pressing Alt-F2 and typing restart)