Good at first, ultimately useless Puntuado con 1 de 5 estrellas
All configuration/settings and layout of buttons of installed addons are not preserved.
All it does is just install the addons, you previously installed.
Full profile backup and OPIE
A "Full profile" backup/restore does preserve your configuration/settings and layout of buttons. To backup/restore your extension settings individually, see the OPIE extension (https://addons.mozilla.org/en-US/firefox/addon/6152 - currently in sandbox)