Microstepping imo is not a reliable method of positioning. Yes it works to a degree but the greatest precision comes from using the steps of the motor directly. I will be using 17's which gives me 200 steps per revolution. Couples with .1 pitch lead screws gives me 2000 steps per inch or a potential vertical resolution of .0005" without microstepping. I don't care to do the math to figure out how the vertical resolution relates to horizontal at the moment, it's been a rough day and I'm a little burnt. I realize that I will have material shrinkage in my prints but that can be compensated for fairly easily IF the machine is built properly and can print repeatably. For instance, a 1% shrink which is typical for ABS means all I have to do is scale my parts to 101%. I don't need half thou accuracy in my prints but I use my printer(s) for prototyping purposes first and trinkets second so accuracy is important to me.
As far as the linear motion itself, acme screws with doubled nuts as I mentioned, industrial rods and bearings, and so on. It's not going to be a cheap build by any stretch of the imagination. I'm guessing somewhere in the area of 1k US by the time I'm done just to buy the parts I need (not including printed parts that I will make on my existing machine). So on par or above the cost of many fully assembled machines but with vastly superior components. Maybe that will translate into a better printer, maybe not. Time will tell I guess.
Part of my design criteria is to fit the power supply under the machine. It means a taller base and a taller machine but a cleaner finished product and one that is easier to situate on a desk and/or transport. The board I haven't decided on a mounting solution for yet. It may live under the machine as well with a fan ducted to outside the frame but I'm still working on the basic mechanical design so I haven't gotten to the electronics yet. The frame is being designed with the intent of closing it off so I can print with whatever I want. I haven't decided on hinged or fully removable panels yet though.