You know, in my opion, Microsoft products and Apple products are entirely different. Even down to the keyboards. I understand Microsoft keyboards/mice are very good, though I do not currently use them. On my PC, I use an Apple keyboard and a Logictech MX revolution mouse. To me, that is the best combination in the market. However, microsoft's hardware has served me excellently over the years.
The 360 is an all-around great gaming device. Though the PS3 is better as far as specs, games cannot even be made yet to fully take advantage of the PS3's power. In due time, my friends, in due time. The bottom line, as others have pointed out, is that windows computers (price wise) are more economical for businesses, most people know how to use a windows computer, and they are "known". Even Windows is not that bad, depending on what you're doing. Though I experience the BSOD at least once a month, (vista/win7) the OS is solid otherwise- for normal internet/photos, etc.
Win7 also has a few nice features, and I'm not even going to lie, the new taskbar is better than the OSX Dock. More functionality, and just as easy to use. I'm thoroughly shocked MS churned out something I like more than the dock.