Rated 2 out of 5 stars
Tried Version 2.1b2, the results
DOES NOT work on Windows XP 32 Bit _at all_ (other then not loading the tabs at startup)
DOES WORK on Windows 7 64 Bit *IF* Load Tabs Progressively 1.6 and Tab Scope 1.1.1 are also installed. The tabs only load (on Win7) if you mouse over the tab and allow the popup from Tab Scope to show, if you click the tab, it will not load and very often the URL will also be removed from the URL field, and you'll have a blank tab (tab lost)
Keep tabs loaded DOES NOT work (WinXP & Win7) (right click 'keep pages from XXXX loaded')
This is one of the best add-on's for firefox, but simply is not working correctly; yet.5 stars when it works.
UPDATE: Installing Compatibility Reporter and setting browser.sessionstore.max_concurrent_tabs to 0 in the about:config gets the add-on working on XP like it does on Win7. But you must use the add-on Tab Scope and allow the popup to show to get the tabs to load when switching, otherwise the tabs will not be loaded and the URL may be lost completely.