Welcome to the new (squeezed down) Office 2011 User Experience 

Click on the image to zoom in
The problem with the ribbon UI (and you can see that clearly in the screenshot) is that it squeezes your work area vertically – a bad thing when screen aspect ratios tend to lean to the wide side, and one of my biggest annoyances when I use Windows on modern laptops (including netbooks, where it’s just ludicrous).
Update: So much so, in fact, that I’ve gone and worked out how much screen real estate you lose from it vertically (over a quarter of the default window size). And you’ll notice there’s no Dock on that screenshot…