Has anybody attempted to port the linux driver that NVIDIA recently
released for accelerated X to NetBSD?

There are basically two parts.  One is the XFree86 module that
does all the real work.  From what I understand, this is supposed
to be OS independent, even on a binary level, so this part should be
easy.
The other part is a kernel driver that initializes the card,
and does various other low level things.  It looks pretty
linux specific, so it would require rewriting large parts of it.

All the source is available at:
ftp://ftp1.detonator.nvidia.com/pub/drivers/english/XFree86_40/

Thanks,

   -Jeff