The simple fact it is a separate window bothers me. I know you can't change the Chrome UI without using C++ but the Firefox version looks and works much better.
Until Chrome lets people modify the browser UI like Tree Style Tab and other addons do, I won't be interested in switching. It's a good browser for my parents, computer labs, etc. but I could never use it on my workstation.
The other simpler addon is not a separate window, but this one is much better once you get used to it. Worth it as it really takes things to a different level.
BTW you can move the tab outliner itself to a tab and close the window.