Argh. After lunch I read that Google Browser Sync is being discontinued, according to a comment at Lifehacker. Since it is just a comment, I'm hoping it is wrong, but given this post at Grant Midwinter, Google may truly be abandoning sync for Firefox 3.
It is probably due to the need to re-write the add-on because FF3 is a new product. Oh well.
But, hey, here's a solution: It looks like Mozilla Labs Weave 0.2 will perform the same functions.