Great addon, the save session (and even group) function is indispensable for me. Every time I launch FF, I need certain tabs open by default. Saving my sessions through this addon lets me load up what I was last working on, and merge in any default tabs that I need. Very good addon, I highly recommend if you want to save your tabs and quickly get back to work. One thing though! This is the only bug I have encountered; The tabs sometimes will stop responding to clicks, and sometimes its not just selecting tabs but specifically moving them (one or the other, though). Simply closing tree tabs, and then clicking on the icon to get it back up fixes the problem. A little annoying but worth the effort since this addon saves me so much time.