Timing Belts?

Hello-

This is my first post to this facinating group. I am am jewelry model-
maker and hope to build a cnc mill sometime in the future. I have
plenty of questions to ask but I'll keep this post brief.

If I ever learn enough to attemp to build my own machine, I would
like the machine to have the following qualities: moderate speed,
high resolution, and accuracy. I have been reading about micro-
stepping as a way to getting higher resolution, however I am
concerned that the micro-steps are really not that accurate.

The alternative to micro-stepping is either gearing down or using
timing belts and pulleys. I realize that ordinary gears can introduce
a certain amount of back-lash into a motion system, and I imagine a
set of gears that reduce or eliminate back-lash can be very
expensive, so I would like to find out if pulleys and belts should be
considered in designing a "tight" system. I have seen steel
reinforced belts, so I imagine stretching of the belt is nothing to
be concerned about, however I am wondering if the teeth on the belts
can introduce some flexing ( resulting in inaccuracies) into the
system?

Thanks for your time-
Tom Murray