I love TreeTabs except for 2 things:
1) Sometimes when I click on a tab, instead of just switching to that tab, that tab and any subordinate tabs open in a completely new window. It seems to happen when I click too hard on the tab. Or maybe there's a very slight movement of the cursor when I click.
2) Then when I move the tab and subordinate tabs back to their original place, the tab order is completely reversed.
Other than those two things, TreeTabs is a wonderful extension! It makes it a lot easier to deal with the many tabs I leave open all the time.