I bought a used one for my use at home while working on a university degree. And as another comment noted, vi would still be usable with a 300 baud (or 1200, I can't quite remember) modem. You could limit the visible "window" into your file to five lines on screen, so it didn't take so long to refresh. Alas, no longer have the ADM3a (but my kids when younger did use it as a play typewriter for a while).