Re: How do I opt users out of this "upgrade" ?
If you're in a business that's Microsoft based then you just hand the entire problem over to IT -- they provide the computer, they make everything work and they're responsible for dealing with any problems.
Meanwhile you use a more realistic system to get actual work done. There are programs that allow you to use your super-spiffy but generally useless Windows system as a terminal (preferably not VNC, though). Computers are cheap and these rollouts typically involve a lot of junking of older but otherwise perfectly usable kit so there's plenty of opportunity to get your hands on a spare system.
Obviously if the company's dumb enough to mandate using Windows despite everything then just find another job. Or just go with the flow, do what you can but make sure you systematically document any problems and interactions with IT so that when the schedule ordure hits the air mover you've got your rear suitably covered.
(NB -- I'm a developer of embedded applications so I have all sorts of needs that don't fit into the traditional IT model.)