This past Christmas, I got the Pan Pastels Painting set as a gift from my husband. I haven't quite "painted" with these yet, but I have been using them in my Art House Co-Op Sketchbook.
So far, as a sketch medium, I give them high marks on a lot of points. First, they blend well. I have the basic artist colors set and the sketches above were done with the basic set. They blend nicely, I have the blending tools set. I tried using a regular cosmetic applicator to see how they would perform, and they work much better with the tools created specifically for these pastels.
Even though they are in a sketch book, they haven't smeared. The Art House Co-Op sketchbook is a Moleskine Cahier thin bound sketchbook and the pan pastels perform well on those thin pages... I can even write over them with my Sakura Micron pens. I can also use pastel pencils over top for more detail.
I like them for spontaneously sketching. I would definitely purchase more pans to add more colors to my palette. I plan to add them to my plein air pastel kit to give me the options to work on regular pastel paper, which I normally don't use because of the lack of tooth, but that's not an issue with pan pastels and I can layer color on top of the base that these pastels provide. What's nice is they blend similarly to how I mix colors in watercolor. I was very impressed with them and really like them.