Fascinating article here , on the Seattle Post-Intelligencer, that quotes Microsoft emails unearthed in the ongoing class-action suit about (alleged) over-promses in Windows Vista (mainly to do with hardware requirements, though the legalities are beyond me). The discussion is very revealing, showing that the company was quite aware of many issues that continue to plague users to this day.
For example, Steven Sinofsky, described in the article as “Windows chief,” notes that older devices were seeing a dearth of device-driver updates. This means that an upgrade to Vista may cost the use of an older but still perfectly-serviceable device, such as a scanner, if the manufacturer doesn’t see the value of developing a whole new driver for Vista.
To me, the value of a new OS would have to be immense, to justify this kind of disruption.