Only Stumbled across this Firefox extension while on the Google homepage at work.
I have multiple installations of firefox ( Desktop / Laptop ) and have been awaiting a tools to help me keep bookmarks on the machines matching.
In all honesty I only require the bookmarks but the other items are a good idea, like saving your last open pages when you closed the browser down so you can conitue browsing on the save machine or another machine. Even the history can be stored.
All of the storable elements have to the option to enable encryption ( defaulted for cookies and stored passwords ).