Non-Windows still has modal update dialog. On startup for non-Windows you are blocked from using the browser until the update is complete. There is a dialog if you run out of date extensions. There is a nag dialog if you have an update pending for over 24h.

What platform? Most Linux distros compile Firefox with "--disable-updater --disable-installer", such that Mozillas auto-update doesn't even exist.

OS X and Mozilla Linux builds.