Of all the softwares I miss the browser sync for firefox the most, when google withdrew the plugin late last year, I thought probably Google was worried about privacy concerns and dropped the plugin. Only after the launch of google chrome I realized the real reason. Maybe Google was little selfish in pulling the plug of a very popular plugin, but then thats how the industry is.
But now Google is launching the plugin again but only this time the plugin will stay much longer thanks to Google chrome. A sneak peek was given in Google's development blog about the launch of the Browser Sync. it is expected to be launched in a week and it will not have all the features of the firefox plugin.
The first beta of the plugin will have ability to synchronise only the bookmarks and later versions will add other features like History,Passwords etc. All these information will be stored under your Google/gmail Account.