This extensions seems nice at first glance, but after using this extension for a while, I view it as being broken. When you open Firefox and you have a lot of tabs already open, you sometime get tab duplication. A lot of the tabs gets duplicated. It makes Firefox very slow to startup. It is unusable in Linux. When you open Firefox, the tabs load without any end. It loads forever and Firefox is unresponsive. So to summarize:

1) Tabs duplication bug
2) Very slow Firefox startup
3) Unusable in Linux, it simply does not work in Linux

I can't rate this extension more than 1.