The interface is easy to use, and the tree toggles off an on quickly. It's great when there are only a few tabs open. My problems with Tree Style Tab is that it slows down and already slow browser (Firefox Quantum). It takes time to load on opening the browser, and if there are more than four or five tabs, it seems to slow down the loading of the pages. This may be due to not being able to override the top tabs Firefox uses, so two sets of tabs are loading at once. Whatever causes the slowdown and freezing--Firefox or the add-on--there are times they simply don't work well together, so I turn off the tree.