One Firefox addon single-handedly changed my browsing experience - Tree Style Tabs. With a little bit of styling & userChrome modification, you get a browsing experience that (a) handles huge numbers of tabs in a sane fashion, (b) takes up only a bit of space on the side, freeing up valuable vertical room & making all your tab names nice and readable, and (c) makes organizing and pruning tabs a snap. It's heavily customizable (but works well out of the box), and it's pretty exclusively for Firefox - similar things for Chrome rely on separate windows and can't remove the top tab bar (making them somewhat redundant).
I also use multiple profiles via Profile Manager pretty frequently - it's super handy to have the ability to launch a clean browser environment for debugging purposes, and to have separate work profiles for different jobs to avoid cross-contamination. Firefox Sync also works quite well between all of my devices, and it's properly end-to-end encrypted for improved security.
I also use multiple profiles via Profile Manager pretty frequently - it's super handy to have the ability to launch a clean browser environment for debugging purposes, and to have separate work profiles for different jobs to avoid cross-contamination. Firefox Sync also works quite well between all of my devices, and it's properly end-to-end encrypted for improved security.