Here's what happened the morning after I played around with the Color Visualizer:
I'm wanting to experiment with a dark ceiling, and this gave me a great idea of what the result might be. The stained bookcases are staying in this room, so I'm going really light with the walls. I couldn't quite get the color as light as I wanted-a creamy white-but I still got a good idea of what the look might be. This room was not even on my re-decorating radar, but it jumped to the head of the line for a minor re-do!