I've had to remind others here at TR many times, when they speak to me as though I know nothing about Windows and am speaking from ignorance, that I'm Microsoft certified and have worked professionally with Windows at least as much as with Linux (though I'm hoping the trend continues and I find myself forced steadily less often to deal with Windows). Almost all professional Linux sysadmins and netadmins came from professional system and network administration of Windows first, and more often than not still deal with Windows professionally.
I found your explanation of circumstances with the systems you oversee to be an interesting case study, by the way. I haven't had the luck to be able to get a clear evaluation of user skill development and platform preference the way you have. Instead, my experience has mostly taught me that people who have worked with Linux and Mac systems for a while threaten to revolt whenever management starts making noises about moving them back to Windows, that my productivity is far greater on Linux than either Mac or Windows desktops, and that my time spent maintaining systems and putting out fires is far greater per Windows system within my area of responsibility than per Linux system (I haven't had Macs inside my area of responsibility enough to really comment personally).
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