Tab Session Manager has been a lifesaver, as Firefox's inbuilt Restore Session frequently doesn't restore all the tabs from the last session and puts tabs in wrong containers - TSM does this all perfectly. One annoyance - tabs restored with TSM seem to display the tab tooltip only once when hovering over a tab. There is no tooltip when hovering over the tab a second time. (I'm using Tree Style Tabs).
Update: discovered that tooltips always appear over over tabs that are in a container, but only once over tabs not in a container.