I keep two instances of Firefox (Release and Nighly) on my work computer (Windows 10), Nightly on my phone (Android) and a couple computers at home running Firefox ESR (Debian). No problem whatsoever, even with such an heterogenous setup.
Do you have any particular need that you think steers from the normal and that Chrome does currently serve? Because for my use case, everything works perfectly.
Yes. Been using it for years. The only gotcha is that adding a new devices loses the date of bookmarks. If you care about that, a workaround is to export and import them.
It is, but it does only work on Firefox (and GNOME Web), so if you want to sync with your phone, you'll have to use Firefox for Android (or iPhone) too. Which is nice as well, and should become a lot speedier in one of the next few releases too.
It's a very nice feature. But note that a consequence of this is that you'll loose data if you desync all devices. The private key is only transferred from device to device, without being stored in any server.
We actually fixed that failure mode three years ago with the release of Firefox Sync 1.5. The encryption key can now be re-derived from your password, so you can always recover your data as long as you remember your password. Even if you lose all of your devices.
We do :) The full details are at https://github.com/mozilla/fxa-auth-server/wiki/onepw-protoc..., but basically we derive two separate keys: one for authentication, that gets sent over the wire, and a completely different one for decrypting the sync key, which is not set over the wire. This means that even if you can observe the entire transaction, you still aren't able to derive the decryption key.
It's more or less:
let quickStretchPW = PBKDF2(email, password)
let authPW = HKDF('authPW', quickStretchPW)
let unwrapBkey = HKDF('unwrapBkey', quickStretchPW)
