I did get the Watersoluble Oil Pastels for Christmas. I have swatched them out and tried a background and stamping with them and I do like them so far.
It is nice to have control over how much blending you get when you color them onto the stamp and then add water, because you can move the color around the stamp with your damp brush and then stamp, which is more control than when you color on the stamp with markers. So I do enjoy these.
I am not sure how easy it will be to stamp over a background, though, since areas are a bit waxy even after you blend it out with water. Maybe StazOn would work better, but I will have to try it out and see.