It was my understanding that Office went to the ribbon because there were new features that didn't naturally fit into the menu bars and the menu bar interface was getting too confusing because there were so many features. With several browsers having simplified their UI, almost to a fault I think, I don't see how a web-browser would need to make use of a ribbon. I am interested to see what they come up with though since I don't think I've seen a ribbon interface used on something that doesn't have a ton of features. I've never been a fan of it in the Office environment but, who knows, maybe the ribbon shines when there aren't a million options and features to cram into it.
If it works, great. If not, there are other browsers.