Thanks for the info- I've been afraid to go rack and pinion so far. I don't really know how much accuracy I need is my main problem, just a fear of not having "enough" and loosing time/money. I'll be declining work from customers in order to build this so I obviously want to get it "right" the first time.
I just got a multi-thousand quote back for all the ball screws, pillow blocks, shafts, etc.... so that is coming as a reality check.
Can you post what your motor sizes are, and what gearing you used? The Shopbot uses 305 oz-in motors with a 3.6:1 gearbox. I didn't count the number of teeth on the pinion though, nor the pitch of their rack.
What kind of top speeds do you get?
Thanks greatly for your help-
Zeph