I've been playing with the program for a while. I was working on a poor quality black and white photograph of a friends father taken in world war 2. It works pretty good, but needs some polish yet. It relies on edge detection to determine the fill areas, so the colors are hard to contain on small areas with fuzzy edges or edges lost in shadows like eyebrows.

There are no metalic colors offered. The array of colors offered for hair, lips, skin, etc. are very limited in range since it seems to be limited to 256 colors, and I have found no way to accurately mix colors.

Going back to change colors or erase areas after colorizing is not possible as far as I can see. Obviously, the program is still beta and can be expected to improve. It has a lot of promise.