Google browser sync
It mostly works, but it’s got rough edges. Syncing is transparent and effective although I have mysteriously lost a couple of cookies. It syncs most of the data you care about except extensions and toolbar layout. Data is encrypted on the client, an essential feature. It’s kind of ugly: the browser button is too big and it pops up annoying alerts if you run simultaneously on two machines.
But there’s one crippling flaw; it adds about five seconds of startup time everytime you launch Firefox. They must be getting a lot of complaint because it says right on the download page “we’re working on it”. Seems simple enough to fix, just don’t sync every time.
What I find most interesting about this is if you squint, Google Browser Sync looks a whole lot like another piece of Microsoft’s Passport/Hailstorm vision. I have no idea what Google’s planning in this area, but it seems obvious to me that people want to centralize a lot of personal data. Google’s proven they can build products that scale and I’d trust them with my data more than any other company. More like this please!