Just upgraded to ff 57, every thing is working great except:
1) ff tab bar not hidden
2) when collapsing a tree it overlaps with the tabs and trees above it. I have to keep all the trees expanded now when using the Metal theme!
---
So for those having the same problem with the metal theme, adding this fixes it:
.tab.collapsed {
margin-top: -24px;
}
.tab {
height: 24px
}

great but now i can't use it on newer firefoxes like 52+

It makes FF57 usable at least(but still missing much functionality). Is there any chance we'll be able to remove default tab bar after installing this addon? Is there webexternsion api to do this? Another thing is that I cannot find a way to move tabs to right instead of left side of the window...