I use echolocation all the time. Granted, I can definitely not explain how a bat feels, but... I was born with 20% vision, and kept it for roughly 6 years. After that, the world officially went dark. However, my brain was quite stubborn in not accepting that. From that point on, my auditory system, in particular echolocation, took over. My internal field of vision did not change much. Echolocation, and my prior knowledge of the world, was used to build up my idea of my surroundings. At first, that built-up internal image resembled very much how I saw the world prior to going blind. However, after a few years, things started to become abstract. I lost almost all notion of clear-cut edges, and color "perception" smeared itself all over the color spectrum. These days, what I see in my minds eye doesnt really reflect what a sighted person would visualize. However, my minds eye still has the same function, it creates my surroundings in my head such that I can navigate and interact with the world.