I like using polymer clay most of the time too!
However I have had fun trying out this Oyumaru stuff - it's playing really - which i think is what it is designed for!!
One advantage over polyclay though is that I don't need a release agent for the mould. Also, it sets firm quickly and can be used at once - no waiting to bake a polyclay mould before using it

You just pop the bars of stuff into near-boiling water till they soften and mould it a bit then take your impression. A big disadvantage for anything larger is that it firms up quite quickly, so really it seems best suited for flat pieces. The instant make and use is extremely appealing though

I trimmed edges with scissors and you can resoften it. The moulds are surprisingly hard.
Here are my quick (unbaked) try-outs - a double-sided bead using a button for the mould and two bits from a mould of a tree charm. Quite a crisp image I think.
