Changing groups just closes all your active tabs and opens the others. So when you switch back, all your tabs reload and you lose history (as in the back or forward button). Pretty pointless. It's about as useful as having a text file with links of your tabs, because you lose your history. This add on should take advantage of the new tabhide in the about:config and maybe that will help it work properly.
Also, even though I restore info from the old tab groups, it didnt bring the history so again i cannot hit back button. shame.