But even when that's true, the answer is still money.
It costs money to upgrade hardware. And to rebuild user desktops. And to retrain users. And to field a lot more help desk calls.
After two years, most big IT shops have already spent money testing important applications to make sure they'll run on Vista. But nobody who's still waiting has launched projects to fix custom apps that didn't pass the test. Those fix-up projects will cost money.
And at most companies, now is not a good time to ask for that money. For deploying a new PC operating system? What's wrong with the old one? No, what's really wrong with the old one -- wrong enough that we can't get by without an upgrade this year?
Then there's the problem of risk -- which also translates into money.