Just one more thing. You put favicons aside, except for pinned tabs. They don't show in normal tabs, nor in the urlbar.
Do you have any reason for that, besides a cleaner look? At least for tabs, its much quicker to change between them just by looking at the favicon, a graphic memory helps identify it.
If you have an article open on a background tab, the article's title usually shows, but since the tab is too small, only the first one or two words will appear, you don't even know if thats a tech article or something about nouvelle cuisine, because you dont even know the website its on. So you will often have to open every tab to know what its about. Or am I missing something?
The dark tab bar background is also quite jarring in the newest iterations of pantheon-terminal. A regression in my view, when compared to the subtle transitions I'm used to seeing in elementary apps/themes. Also, having the new tabs button on the left has the unfortunate repercussion (within pantheon-terminal) of having three controls (close window, close tab and new tab) within extreme close proximity. Of course, this is only true for pantheon-terminal AFAIK, owing to the unique conflagration of a tabbed UI and no toolbar separating the window controls from the tab controls.
I do hope you chaps opt for tabs-on-top eventually. Of course this won't solve the above issues (unless such a move were to come hand in hand with moving the new tab button to the right and styling changes), but the look so much better than tabs-on-bottom and hanging-tabs (or inverted tabs, if that's the more proper jargon).
Looks great, but I wonder what you'll do with the windowbars that doesn't have such a toolbar... At jupiter it looks always like an ugly cut when there are no toolbars for example at the terminal (with hidden toolbar). This here would be really a waste of space... Whish it would be already usable