Over the years, I've worked with and regularly used countless OSs, been a systems programmer working with several OSs, and worked with countless different architectures. From HUGE computers, to small things.
These days, I'd say I'm most familiar (from a day-to-day and GUI perspective) with Windows, but equally at home with command-line Unix (/Unices).
I've never really bought into the polarisation that some seem to cling to. If I look back at the years, happily spent on big Unix systems, even that is predated by the years I spent happily working with even bigger mainframes.
For all the times I've seen people boasting about Macs "just working" and "don't have to worry about virusesssesssess", I'm reminded of times when I've had to fight integrating Macs and other Unices with other networks / directories / OSs, and vice versa. There's rarely a moral or technical highground in this, just shades of preferences - and in some cases, fashion, image, and bandwagon.