Microsoft has dedicated a whole website to try to convince people that Vista isn't so bad after all. The problem actually repeats one of Keough's descriptions of how he fell for replacing Coca-Cola with New Coke. His commandment is trusting outside experts, but what you really see is with New Coke you had user studies that showed people liked New Coke more in blind taste tests. What they missed is that people had an emotional connection with the old Coke, regardless of the sweeter taste.
Here Microsoft is missing that the issue with Vista is not the usability in a vacuum, it is what happens when you try to get it work with your legacy applications and hardware. No drivers, problems, upgrades required, and so on and so on. They don't test for that in their experiment.
This study has all the feel of some attempt at internal political justification, and not actually marketing a product anyone wants.
And I say this as someone who runs Vista and has no issue with it.