Why settle? Three years ago, research firm Forrester said "Windows is the only desktop you need support."

Not any more.

In a report released yesterday, analyst David Johnson recommended that IT departments should formally support Macs as well because the best employees prefer them and are bringing them to work anyway.

As Fortune first reported yesterday, Johnson called Mac users the "heavy hitters" and "heroes" in organizations, and said that they hate Windows PCs because they slow them down and look cheap. "Stand in the way," he warns IT departments, "and you will get run over."

Those are matters of opinion.

But the report also contains some data and anecdotes that should make Microsoft and its PC partners nervous.

Mac use is growing. 22% of organizations expect Mac use (not iPad use) to increase at their place of business within the next 12 months. Only 3% expect it to decline. (Based on a survey of 590 IT departments and decision makers in the US and Europe.)

Companies may not be willing to pay the Mac premium, but employees are. IT departments don't usually buy Macs, but high-level employees who can afford to bring their own computer to work are often choosing Macs. "There is a strong correlation between higher corporate average salaries and the number of Macs purchased by employees and brought to the office."

These employees tend to be the richest and most productive. Forrester suggests that the typical Mac user fits in the segment it calls "power laptop" users, who work an average of 45 hours a week and make 44% more money. "Most of the Macs today are being freewheeled into the office by executives, top sales reps, and other workaholics."

Johnson says that this is just the first report that will introduce IT departments to this new class of Mac users.