The reborn bar replacing the extension bar poses a problem.
Whereas the extension bar lived below the address bar, the reborn bar lays on top of everything and when expanded to show an extension panel, it would steal quite a bit of space from the tabs and address bar.
This is particularly egregious at lower resolutions, such as the typical 1366x768 of most run off the mill, cheap-ish Notebooks.
Also it messes with your muscle memory, because it moves around the navigation controls every time you switch.
I would really, really, like an option to confine the reborn bar below the address bar.
I tend to keep my (V7 extension) bookmarks visible and while real estate is at a premium, this new layout messes up my work-flow.
This is my browser window right now, in Opera 53:
*(I still use Opera 53 due to a longstanding bug that disables subpixel font rendering in opera internal pages and interface.)
This is what it would be reduced to, with the reborn bar:
And there are only 22 Tabs. Imagine with 100+...