Hacker News Reader

Does it only count if it's native rather than an extension?

What do you mean killed it? I use a different addon for vertical tabs (there are many now) but isn't it still available?

Tree style tabs works as well as it did before, except that it's more difficult to get rid of the top tabs.

Check out my userChrome changes if you're into vertical tabs and a minimal UI: https://github.com/bjesus/fireside