<I>Do MS actually ask any real users what they think of new features/behaviour?</I>

Yes.

Now the next part defines a user:
A typical user composing most of Microsofts market will be the person who simply uses their computer. They are definitely not a power user, and never stray into anything remotely close to TweakUI. (And they would never go into the registry). These people are the ones who install tons of software packages, and never clean up after them. Thus their start menu is huge, and at their resolution, is probably scrolling, or dual layered depending on what Windows they have. So these people are the ones that like these type of features. For the Start Menu, it makes sense for those who don't clean it up or organize it. In Office though, it doesn't make much sense to me. The menus never change, so why hide them?