I was someone who installed the first beta of Windows that included this, just to try it out for Rails. It had LOTS of problems. I filed bugs. I kept trying over the next couple of versions, and finally gave up. I tried it again a few months ago, and, again, ran into a show-stopping problem of some sort, and gave up again. Are you saying that you use it "in anger" for serious development, and have no issues?

People complain about doing Rails on Windows, and, while there's definitely extra friction, and I hate Windows in general, I have really good luck with RubyInstaller. I used to have a hard time with ExecJS, but now I just install Node (on either Mac or Windows), and I'm usually off and running.