I agree with ya there. I haven’t really looked into many of the changes in Vista to prevent attacks, but I have heard from knowledgeable professors that there have been many improvements. Microsoft knows where their downfalls lie within XP, they’re not stupid.
People def. target Windows OSs more, but as you said, large corporations use unix OSs to run their servers and so its definitely somewhat of a target. Also, lately(from what I have noticed, could be wrong) a lot of companies are turning to open source unix/linux solutions. So that may change.