I saw some Channel 9 interviews with Vista programmers who were proud of the
new I/O cancellation features in Vista.
So why is Windows still refusing to close a non-responsive task in task
manager when I tell it to?

The program is a video capture tool written by Sony, to capture video
streamed over USB from my Sony camcorder. It talks to a device driver which
was also written by Sony. While streaming video (but not actually capturing
to disk; just displaying it in a window on my desktop), I accidentally
unplugged the USB cable. The capture program froze. I reconnected the USB
cable, but the program stayed frozen. I pressed the red X in the title bar,
and nothing happened. I tried closing it from task manager, and Windows
asked for the standard confirmation that I really want to kill the program,
and yet nothing happened. I tried rebooting Vista, but it wouldn't even shut
down; it closed most of the desktop, but left the capture program on the
screen, and refused to finish shutting down. I could still move the mouse
cursor, but ctrl-alt-del did nothing. I had to hard reset the machine.

I thought that Vista had a redesigned driver architecture so that
misbehaving third party drivers couldn't screw up the machine like this
anymore.