Experimental psychologists have found there is a threshold below which a change in a stimulus, such as the loudness of a sound or the brightness of a light, goes unnoticed. This was codified in the 1800s into an equation called the Weber-Fechner law. Berger's algorithm applies this law to the brightness of single pixels in a video image. A common method of compressing video is to transmit only information about the pixels that change from one frame to the next. CU30 transmits those changed pixels only when the change is great enough that a human observer will notice it.
Edges tend to be sharper than in other systems.
It doesn't matter much on a wall, but it can show up in close-ups of a face. For videoconferencing this doesn't seem to bother most people. But in TV or a motion picture, I don't think you would like it.