Agreed - servos are the better way to go. Considering the needed size, they ought to be cheap enough. The biggest problem I have with servos is me.... I know absolutely nothing about setting them up. Steppers I know but I will not discount servos.
After a discussion with another friend, that is also considering a build of his own, we have decided that we really should look at belts vs. racks. I am theoritically ok with belts, as long as I do not deal with screws (did that once & prefer other methods of motion)....... No offense to those that use screws, just a personal preference.
Will the Retina work with servos? I am stuck on that thing - very impressive. Btw...are they still possibly looking for beta testers??