When feeling creative, don't fight it. A comment from Augusto asked what the Tabs and History would look like in the Firefox exploration. My initial answer is 'I don't know.' While that's still true I did decide to do a quick exploration to satisfy my own curiosity:
The little buttons along the left are for creating a new tab or closing the current tab. If the screen was larger (or if I was showing less open tabs) the labels for these controls would be shown. This shows the gallery style control that's used across Office 2007. The gallery control allows you to expand the gallery as a drop-down to show a full grid of available options.
This type of design does bring up some interaction questions... Does it make sense to automatically bring the user to the 'Browse' tab when they create a new tab? Is it important to show the location area when using tabs? Is 'tabs' an appropriate name for what amounts to multiple open documents and not actually tabs? I'm sure this creates as many answers as questions but it does illustrate the gallery style and how the Office metaphor could be used within a browser for features beyond basic browsing.