So, what's this then, for all Mozilla users? From the horse's mouth:

Google Browser Sync for Firefox is an extension that continuously synchronizes your browser settings ““ including bookmarks, history, persistent cookies, and saved passwords ““ across your computers

Mouth-watering as it may seem, do keep in mind that Google do what they will with your data. The following quote, taken from their privacy info-page, is interesting though:

You can choose to encrypt Google's stored copies of your settings.

Does that mean that not even Google can eye your secret data?

As usual, read their privacy policy and remind yourself that sentences such as:

We offer some of our services in connection with other web sites. Personal information that you provide to those sites may be sent to Google in order to deliver the service. We process such information in accordance with this Policy. The affiliated sites may have different privacy practices and we encourage you to read their privacy policies.

..and what about:

This Privacy Policy applies to web sites and services that are owned and operated by Google. We do not exercise control over the sites displayed as search results or links from within our various services. These other sites may place their own cookies or other files on your computer, collect data or solicit personal information from you.

...also, interesting:

We may process personal information to provide our own services. In some cases, we may process personal information on behalf of and according to the instructions of a third party, such as our advertising partners.

Mmm, I lervs a bit of my life shared with third parties. I love parties. Or you could download MS Windows Vista beta 2 instead.

edit: there is now detailed info on the installation-process from Lifehacker.