Given the severity and commonality of flaws in (early, especially) builds of Windows, it's almost a miracle the Internet is still running, seeing how that is by far the most common client OS and makes up a reasonable proportion of server OSes.

When something seems to be almost a miracle, I look for other causes.

I'm not going to claim that there's any sort of moral high ground to be had in the sort of IP protection that goes on for closed-source type companies, but I do feel that for being the brightly lit, golden-walled house on the hilltop, Windows has done an amazing job of handling security.