Sync does "sync over" bookmarks folders. Over a few days of use on each device, all installations sh

Sync does "sync over" bookmarks folders. Over a few days of use on each device, all installations should equalize and become pretty much the same. The main difference with Sync as far as bookmarks are concerned is on "mobile" versions of Sync. On desktop and laptop Firefox installations Sync should make all installations almost identical; the only real differences would be with Recently Bookmarked bookmarks. And possibly the Bookmarks Toolbar folder, which if they are purposely different with the initial sync per device, they might stay that way. Sorry I have been unable to verify that in recent versions as I no longer have multiple devices to test Sync with. My other PC died about the time a change for "mobile" devices that was made and that may have affected "desktop", too.

But Sync is not 100% with extensions as they're not really synchronized. Sync installs extensions afresh and only those that are hosted at AMO. And the synchronization of preferences for complicated extensions can be a royal "pain"; there could be the need for the user to manually activate the synchronization per preference. Some extensions have hidden prefs (in about:config) that aren't documented well if at all. leaving the user a lot of digging and guessing to get sync to work completely for the particular extension.