Just look at it in a practical way: if I want to test ma Webpages, created on my Mac, it's very usefull to test it via Parallels with InternetExplorer - it's just a shortcut. I don't need to install Networks, boot a noisy PC an switch keyboards etc. Just one machine for everything. As long as Windows Apps behave different than others there's no other way than testin your Code in Windows. I don't have to use e-Mail or other things - so it prevents me from getting a worm or virus.