Machining smooth Curves

I really don't know that much about this subject, but have seen
references to NURBS and bezier CAM controls, which sound very
interesting for smooth, fast machining.
I use bezier curve toolpaths prior to producing G-Code from them as a
large number of small segments, outputting the actual curve would
appear easier, more accurate and faster than converting to linear
moves or even a series of arcs.
It would seem to make sense to interpolate a curve at the time that
the step/direction signals are being generated rather than at the G-
code stage, as although the curve would still be composed of small
linear steps, the resolution would be at the very limit of what your
CNC machine could handle.
Are there any motor driver control programs that work with curves
instead ( or as well as G-Code ) ?

Rab,
Rainnea Graphics

PS. I've put some more stuff on my web page if anyone's interested in
my CNC Taig Mill: www.project.rainnea.com