Is it the point of an OS to present problems which have to be overcome, or to be the answer to more efficient and esthetic computing?
The point of an OS is so that you don't have to interact with hardware directly. It provides a layer between you and the hardware to make using that hardware more useful. The "problems which have to be overcome" that inevitably present themselves seem to be (mostly) in one of two categories: limitations or unintended consequences.
Limitations could be hardware based, as in technology isn't advanced enough at the time of release, or software based, as in having to support legacy APIs, etc.
Unintended consequences are the trickier ones. Looking at the reasoning behind removing the start menu, Microsoft stated that its usage had dropped by 11% between Vista and 7. This was attributed to things like the being able to pin to the taskbar, which is fine, but the usage didn't drop to zero.
The biggest thing they didn't think about was what it was still used for. My theory is that it's now used more often when someone doesn't know where something is, so that's where they START (get it?) to look when they try to find it. Without that single point of connection to their computer, what they're faced with is a mish-mash of different places where only some things are, and that's where a big portion of the userbase is going to be alienated. They've taken out a release valve for confusion.
Microsoft looked at the frequency of usage, but not the importance of usage.