Shopbot, Rack and Pinion, Ball Screw, Acme precision screw?

I am going to the Shopbot dog and pony show next week in Durham, NC
to see what their machine can do. If it doesn't measure up to my
expectations, I need to know if anybody knows if Acme precision
screws will work reasonably well when compared to ball screws? Ball
screw manufacturers really make you grab your ankles hard when
quoting a price.

Do rack and pinion systems work well? If so, who sells them? I'd
kind of like to find a site that gives prices so that I can price
without having to get a quote.

Thanks,
Wes