It seems eBay have gone the whole hog and made available a Firefox eBay Edition, at http://pages.ebay.co.uk/firefox/. It kinda beats "download Firefox with Google Toolbar", and I wonder whether we will see a "Firefox Google edition" in the future?

It's just an extension that alerts you of items you are watching. It's been around for about a month.

Google has quite a few Firefox extensions: http://www.google.com/tools/firefox/

I've been expecting Google to update Firefox with Google Toolbar to also have a few other Google Extensions, so basically "Firefox Google Edition".