linear bearings, Ball screws are the way to go knowing what I've gone through now. You'll want all the precision and repeatability you can get. If its in your budget then I'd say, yes go for it. If not just stick with Acme screws and box ways, Its all in good fun.
http://www.cnccookbook.com/img/Other...lete_assm2.jpg http://www.cnccookbook.com/img/Other...ldIMG_6396.JPG
Nice start for a CNC lathe. Would like to be doing the same but for a 3 axis mill.