Don't mix up things. Directory service is one thing, user-facing OS another. You want to stay on Active-Directory ? Why not. You want to connect Macs, Linux or whatever to AD ? Why not. The mileage of effort to bind a workstation to AD will vary but it's mostly possible. So why is people still using Windows instead of Mac OS or Linux ? I personally think because they are used of it and they know nothing else. Buy a new PC and it will have Windows preinstalled on it, go work somewhere and you will probably find a Windows workstation. Switching between Windows and Mac is quite easy, the differences from the user perspective are not so big. Linux as workstation is still not a real valid competitor, although the community is doing a great job and is keeping up. What about the price ? Is time to stop comparing cheap-bad-ass hardware running Windows with Macs ! Get a notebook with similar HW performance of a MacBook and compare the prices including OS: where is the difference ? So finally as end-user we are driven by companies selling us bundles of HW with Windows on it and as workers we are hired by companies with Windows administrators dictating the OS to use.