I'm coming from Tab Tree (and Tree Style Tab before) myself :)
I really like the compact list of Tab Tree, so that's what I wanted to reproduce.

Audio button should be in v0.3, I've implemented the feature.

Tree feature is not yet possible (maybe in a later firefox version? See here for details: https://github.com/idlewan/vertigo-tabs#to-not-do-yet ).

Close button might be good to have, but since I don't use it myself (I only use ctrl-w), I might wait for someone to do a pull request. It would require having an option page, which isn't done for now because not necessary yet.

Have you seen Tab Center Redux (made by another developer)? Maybe it would fit your needs: https://addons.mozilla.org/en-US/firefox/addon/tab-center-redux/