>>3085486I call it "being capable of being used in half decent fiction". Well, as half decent as any fiction involving Rifts could get.
As to my personal thoughts on them, my only complaint with the concept lies with the people who play them. Juicers in fluff are usually either manic thrill seekers with way to strong a sense of immortality or butchers with too many drugs going through them. Unfortunately, when in the hands of players, they tend to become dour, tragic super soldiers.