Some users do have difficulties with Vista, whilst others are very satisfied with it. Of course, satisfied users are what all of the users should be, so the fact that substantial number of people are dissatisfied with Vista, might indicate that this new operating system is not meeting all needs, or working satisfactorily with some applications. I am aware that Microsoft do not always allow for backward compatibility, and that also may be a part of the problem.
In any case, it does not cast Microsoft in a good light, if a new operating system is not providing a suitable platform for all users and their applications.
This probably has quite lot to do with the fact that Microsoft is so big--almost a monopoly--that they do not regard it necessary to provide anything better. After all, if it is plain unsatisfactory, what are you going to be able to do to fix it, anyway? Choose another O/S?