Gestures, "search with" context menu, "add active tab" in a bookmarks bar folder, autorenaming downloads, custom keybindings, tab squeezing (it keeps them wide and shows scroll buttons), last tab standing, proper double-click-drag selection and text editing in general. Probably a dozen more things that I cannot remember now. Also "sync" just doesn't work, something went wrong, try again.
For gestures I used Gesturefy - isn't a mess and has "rocker". For "search with" I just had to write my own extension with hardcoded searches. I'm autorenaming through AHK - external tool, non-general use case. Tab squeezing and last tab solved through about:config.
"Add active tab", custom keys, text editing still unsolved.
In general I'm sort of satisfied with the results, but it took quite a while to migrate. Firefox is sort of extensible but not hacker-ish. Extension store is not generic-developer-hacker spirited either. FF is almost as dumb as Chrome, with a few settings that can make it better if you know where to look and have time for that.