The New York Times has a piercing analysis of documents from the Vista capable lawsuit. The documents show that M$ broke things at the last moment.
"Late OS code changes broke drivers and applications, forcing key commodities to miss launch or limp out with issues," said one slide in a Dell presentation dated March 25, 2007, about two months after Vista's launch at retail and availability on new PCs.
We have all heard the lazy vendors don't believe Vista will launch excuses but few of us have heard Steven Sinofsky, chief of Windows development, second and third opinions.
"Massive changes in the underpinnings for video and audio really led to a poor experience at RTM," he said. "This change led to incompatibilities. For example, you don't get Aero with an XP driver, but your card might not (ever) have a Vista driver." Finally, said Sinofsky, other changes in Vista blocked Windows XP drivers altogether. "This is across the board for printers, scanners, WAN, accessories and so on. Many of the associated applets don't run within the constraints of the security model or the new video/audio driver models."
Continued attempts to blame vendors for M$ changes are disgusting. Up to RTM things worked, so vendors had every right to be complacent.