I'm curious about this stuff and its cousins and also how it plays with polymer clay.  Does it stick well to cured clay?  What's its best use?  What other brands/sources are there for this kind of moldable, stickable epoxy-type material?

I don't know how this stuff plays with PC but there have been two part epoxy product similar to this for some time. My son builds miniature game pieces and they have a two part sculpting epoxy, green stuff, that is used to modify the little people. There is also products called plastic steel and plastic aluminum that work much the same way. These all stick to just about anything that is clean and dry so after reading about this Ferido product I think that it will work much the same. I just don't know how firm the bond will be.