Unfortunately, they started from stratch with Chromium-Opera, and even after more than 10 versions it still lacks most of the great features of Opera.
Day to day, I use both Firefox with Tree Style Tab, and Chromium with Tabs Outliner. This isn't perfect: Firefox still takes a minute to load the session with 700+ tabs, and Tabs Outliner feels kind of a hack and isn't really integrated.
Hold right click and scroll your mouse wheel down (you have to tweak a setting to have scrolling up also bring up the menu). Your tabs will appear where your cursor is as a drop down list, sort of like a context menu.
Combined with tab groups (ctrl+shift+e, or make another mouse gesture) and I can sort my tabs into categories and quickly switch between my tabs by either switching tab groups or using my mouse wheel, no matter where my cursor is.
So much time saved from not having to go to the top/side of my browser to switch tabs. :)
E:
The setting is under "Advanced" -> "Wheel Gestures" and the action is "[Popup] List all tabs"
They've completely disregarded the possibility that the lack of effective tab management is limiting most users to use only a tiny number of tabs.
Tree Style Tabs for Firefox has been an integral part of my browsing experience ever since I discovered it: http://i.imgur.com/PnpZwos.png
I just wish some browser vendor would release an official vertical tabs solution that had a more seamless implementation of autohide/autoexpand (for non-maximized windows where horizontal space is at a premium).