I have about 20-30 tabs opened in my computer (under Ubuntu), and a fresh installation of Windows XP in my laptop. Both have the last version of Firefox.
I used the option for replacing data in other devices with the existing data in my computer. It seems to sync for several minutes (the button have an animation), first in my computer and then in my laptop when I open the browser.
I get all my data synced except for opened tabs.
Also, do Sync take into account the groups of tabs? I usually organize my opened tabs in groups when I'm working in several topics. I'd like to have that exact organization in my two machines.