CAD software makes use of OpenGL to create those interactive, fully-rendered, real-time zoom-and-pan 3D graphics of complex models. There is some early indication that the next release of Windows breaks OpenGL.
Over at the offical OpenGL discussion forum, administrator Metro reports that Windows Vista is layering OpenGL over Direct3D. For CAD users, this means that:
"* OpenGL performance will be significantly reduced - perhaps as much as 50%
* OpenGL on Windows will be fixed at a vanilla version of OpenGL 1.4
* No extensions will be possible to expose future hardware innovations"
It is possible to resurect OpenGL to its full performance, but that means the loss of the "eye candy" effects on the Vista desktop.
The other possibility for CAD vendors is to rewrite their software to work with Microsoft's proprietary display interface -- possible, but unlikely due to the cost, time, and danger of breaking the software, all for a very small market.
"Meanwhile, Cringefan Ken M. points out that VISTA is really an acronym for Viruses, Infections, Spyware, Trojans, and Adware. That’s clarity for you." - ROBERT X. CRINGELY