Those who succeed in this practice attain a state of radical freedom: there are no boundaries, no presuppositions, and no habits on which to rely. One perceives things as they are in their naked reality. Ordinary beings view phenomena through a lens clouded by concepts and preconceptions, and most of the world is overlooked or ignored.
The mind of the great perfection adept, however, is unbounded, and everything is possible. For many beginners, this prospect is profoundly disquieting, because since beginningless time we have been constricted by rules, laws, assumptions, and precious actions. One who is awakened, however, transcends all such limitations; there is no ground on which to stand, no limits, nothing that must be done, and no prohibitions. This awareness is bottomless, unfathomable, immeasurable, permeated by joy, unboundedness, and exhilaration. One is utterly free, and one's state of mind is as expansive as space. Those who attain this level of awareness also transcend physicality and manifest the "rainbow body" ('ja lus), a form comprising pure light that cannot decay, which has no physical aspects, and which is coterminous with the nature of mind.
--from "A Concise Introduction to Tibetan Buddhism", by John Powers
Snow Lion Publications
illustration, Tibetan letter A, the symbol for the Body of Light