I worked on device connectivity in Windows core OS division in the Longhorn/Vista push. I came from the Linux and SunOS world before that. It was simply crazy at the dedication and effort put in to make Windows backwards compatible with whatever old broken and poorly behaving USB and printer device. We would have no-named cheap web cams that didn't function to USB spec but "worked" in Windows 98 that needed to work in Vista while still implementing new secure driver models that broke all cheap device assumptions. It was a long hard trek to get all those devices working.