Okay, and here is what I don’t get about the ongoing nix-declarative enthusiasm:
How does this deal with your passwords, history, bookmarks, etc? And if it doesn’t what’s the big deal? What do I get out of this that wouldn’t be better with Firefox sync?
I personally use both. I use Firefox Sync to handle syncing of data I’d consider owned by the browser (history, open tabs, bookmarks). I don’t, however, consider it my browser’s job to own & manage my passwords. I keep those elsewhere and manage them separately.
I wouldn’t say this is “a big deal”, nor a particularly strong purveyor of “the ongoing nix-declarative enthusiasm”.
This is just a write up of a few behaviours I wanted from Firefox that could be expressed in a stable, repeatable, and fairly elegant manner using Nix. Firefox Sync will not give you the profile management approach I wrote about, nor will it sync your userChrome.css, or even all of your about:config settings.
Two follow-up questions, if I may: