Tim,
You view the world through your Microsoft-glasses. Why is Microsoft the standard for interoperability?
If your need is for a language, you have Java, which runs on any OS unchanged.
If your need is for a web protocol, you have HTML, which runs on any OS unchanged.
If your need is for [holding my nose] .doc documents, you have Open Office.
When I switched from Windows to a Mac, I had absolutely ZERO compatibility issues.
When the large multi-national corporation I work for switched all its developers from Windows to Mac, our productivity skyrocketed.
Windows is such a piece of crap that its users assume that the constant threat of viruses, trojans and other malware is just part of life. In fact, it's part of the terrible architecture that is Windows.
I disagree 1000% with your premise that Windows is the only way to universal compatibility.