I started building http://www.openbuilds.com/builds/emmett-delta.3052/ last Winter & using EMT for the horizontals. After wasting a couple of rolls of filament of testing different Vertices, I decided it was not worth the effort to me. I did learn a lot from working on this. I was going to use 2060 or 2040 V-Slot for the verticals, but I did create a vertex that would use 4x 1/2″ EMT. Here is the idea I had for using wheels with that. http://www.thingiverse.com/thing:1149428 You can also use these less expensive nylon wheels https://folgertech.com/products/nylon-roller-wheel-used-on-rev-b-kossel . You can also find those on ebay, but that was the quickest link to them I could think about.
I just finished building a Folger Tech Kossel 2020 https://folgertech.com/collections/3d-printer-full-kits/products/folger-tech-kossel-2020-full-3d-printer-kit that is working quite well. For $326+Shipping (probably $400 total with the extras I added), I can not believe how well it prints, in most cases better than my Makerfarm i3v 10″. I spent about 6 weeks building it, but I was also redesigning some of the plastic parts that I did not think worked well. I might build another Delta this winter, but use V-Slot & 32bit electronics. I also saw this idea for using bearings on 2020, but you might could adapt it to use with EMT. http://www.thingiverse.com/thing:1630978