Great examples. I find them even more valuable for removing reflections than for color saturation.
Another fun use: If you have a B&W composition in mind, you can use polarizers to bring out nice pure colors in part of the photo, with the idea of eventually turning them dark black or bright white. For example, by making the sky really blue in the original here, I was able to remove the blue channel and turn the sky deep black as a result. Without the polarizer, the sky would have been too mixed, and would have come out grey.
