It puts tabs on the side, where they take up low-value horizontal screen space instead of high-value vertical screen space. And you can read the tab titles them even if you have lots of tabs open. And it groups them into trees -- links opened with a middle-click from one tab become children of that tab -- and you can collapse/expand trees.
Wow, just trying it now. So much better than existing tabs. I suspect it's going to take a lot to rewire my brain to use this, but it's clearly worth it.
I rarely collapse sub-trees; I rarely have enough tabs open for that to be needed. And I set the prefs so that if I close a parent, the first child takes over as the parent of the tree.
