Couple that with some flavor of Linux and you really can get out from under the Redmond Beast.
Also works with macos, btw :). I have a couple of friends who are already "living Linux" (read: Linux desktop), but when we tried that in our office it just wasn't feasible. Apart from LibreOffice and, at a stretch, Thunderbird there isn't that much quality desktop software and we do need to get work done.
Sure, you can eventually get people going on things like GIMP and Scribus but we found it easier just to give them a Mac or a Macbook and be done with it - easy to manage, good overall cost profile and fairly simple to secure. As desktops go, they do the job very well and people generally take to them in days, even if they have been using Windows for years.
That said, when it comes to servers I wouldn't use macos because, umm, how do I say this gently, macos utterly *sucks* there :). We use Linux there, plus the odd FreeBSD deployment to break up cascade failure risks where they would affect critical systems (the nice thing with a lot of FOSS tools is that they don't care that much what platform you run them on).