I guess it's not a secret to anyone that many people complain about Vista, they simply hate it, they post negative comments on the web forums and so on. But are those complaints reasonable? These thing started to happen not after the Vista release, but some time before that! So, when Vista finally came out, it already had a negative image and it still has, no matter if it's a really good operating system. For instance, I know some people who are going to buy a laptop but they are scared to death by Vista, that sounds ridiculous and even stupid, but that's a fact. They don't want to have Windows Vista installed on their laptop instead they are trying to find one with XP installed.
It doesn't have anything to do with Vista qualities, only with its image as a faulty, unstable OS, where many applications don't work and your hardware don't work as well. Of course, it's not true, however that is the image of the OS. Although Microsoft says that Windows Vista sales are pretty ok, that image hurts it.
The same thing applies to Internet Explorer. Although IE8 has successfully passed the Acid Test, it is still considered to be a piece of junk, even though Microsoft deliberately issued a beta version for web developers who can play with it, who can tweak their web sites if they are not properly displayed in IE 8.
So, even though Microsoft release really good products, unfortunately they cannot get over their bad image. However, this applies only to the masses, because the IT professionals are usually better aware of the real quality of the Microsoft products.