My concern with that mulch is.... what happens when it gets mixed in with the soil. You'd never get the lumps of rubber out of your garden again? Then again, I suppose the same goes for gravel or stone mulch. 
This would be my objection too. I have got some parts of a thirty years old houshold waste heap in the soil of a part of the garden. The parts that are paper, food left overs etc are fine but the plastic shreds need to be laborioulsy sieved out. I find also the expanded clay pellets that come with some pot plants to be a nuisance.
Göte
