I know quite a few RoR/Java/Linux/Unix sys admins who still use Windows on the desktop (inc. me).
OS choice shouldn't be a deal breaker.
Is having a Windows Phone also a deal breaker?
As a side point, is there really that much difference between OSX/Windows now a days? I've have Macbook Pro's, Imacs and Windows things as main machines and nowadays I don't see that much difference between them (esp if you're working on web dev). From Mac -> Windows or back seems like just a new novelty tech to learn not a deal breaker any more. From your article it seems unlikely that Mac OSX or Windows is running your servers anyway.
(Same with Android vs iPhone - both are so similar now)