Totally, I mean you pretty much have to be on Windows to be a good .NET developer (unless you're big on Mono or whatever).
It sounds like the OP is interested in working with "latest and greatest" web technologies, though (no offense), and many of them are developed on Macs or Linux and therefore the best development environment for them is on a Mac or Linux machine.
I think it might just be a culture fit thing, as some people gravitate to .NET type stuff and some people gravitate to node.js or Rails, and just as it's a pain in the ass to get .NET stuff working on a Mac, it's often a pain in the ass to get things like Rails or node.js working on Windows.
It sounds like the OP is interested in working with "latest and greatest" web technologies, though (no offense), and many of them are developed on Macs or Linux and therefore the best development environment for them is on a Mac or Linux machine.
I think it might just be a culture fit thing, as some people gravitate to .NET type stuff and some people gravitate to node.js or Rails, and just as it's a pain in the ass to get .NET stuff working on a Mac, it's often a pain in the ass to get things like Rails or node.js working on Windows.