Yes I have tried them out. They are awesome. You can cover large areas with the limited efforts. And unlike "tradtional" pastels, they get fixed quite effectively, retaining the same hues as applied.
Still experimenting with these, especially on how to get the minute details, so sometimes I go over with soft pastels or pastel-pencils.
If you have a background made out from this medium, (once fixed) it also relatively easy to go over it with markers, other pastels, pencils etc.
If you check their website out, there are some examples of other artists who make use of them - and they are stunning.
The only problem I found is that you have to air them once in a while; I live on an island, surrounded by sea... so the humidity sometimes sky rockets - so it is a common nuisance to open a tub/pan/pot/tube and find white-growth in.
i have them on my wishlist. lol