They should probably ditch all in-memory stuff, and just use the drive, so they can support those cases when you really want to have a "low millions of tabs open."
>Chrome's tab UI makes more tabs completely unusable
True, thankfully we have extensions that deal with this (I've been using Keepin' Tabs for this, until I started using cVim)
When I have 20 open I already start to get confused about where stuff is...
* Firefox's Awesomebar (the address bar) is much more powerful. Whereas Chromes sends you to google mainly: https://support.mozilla.org/en-US/kb/awesome-bar-search-fire...
* Tree Style Tab: https://addons.mozilla.org/de/firefox/addon/tree-style-tab/
Thanks to Firefox's userChrome.css, you can pull pretty nice customized UIs even without any additional extensions :) https://github.com/eoger/tabcenter-redux/wiki/Custom-CSS-Twe...
I have 9 virtual desktops; I typically have browsers in 6-7 of them for various in-progress tasks. That's somewhere between 6 and 14 browser windows (I can fit two side by side on my screen), with multiple tabs in each.
Finding things is easy. Even ignoring the per-task categorization by desktop, Firefox lets you search all your tab titles/urls: just type "% " in the URL bar followed by your search string. If I'm looking for something specific, this is the simplest way to find it.