gui design – Microsoft Visual Studio 11 – why would they use uppercase in UI?

Microsoft has been very transparent with their updates to Visual Studio 11. It includes a huge change to the UI design of the entire IDE, most notably colour themes, icons and capitlization.
In their original announcement post with screenshots, many users hated the design and cried for them to bring back colour and to not use all-caps in the menus/panels.

Today, they posted screenshots of the release candidate which has some of these requests implementted, but they also chose to uppercase the main menu.

As a programmer (i.e. not a UX expert) I am wondering what their thought process might be on choosing these design options. To me it does look clean, but to many other developers (as noted in the comments) they reject it entirely. What are considerations in designing a complex UI such as this and are there any studies/examples that indicate these are good choices?