I briefly tried it (as an indie game developer). It's basically taking a metaball approach to modeling and performing some form of real time rendering so you can see what the result will look like. It also allows you to add some animation and what-not.

Overall I don't see it replacing any serious tool at the moment, its quite slow in modeling (because of the rendering) and precision.

What it can be useful for is if someone doesn't have the necessary tools/skills and they just want to make a basic and quick 3d shape like a smiley face, have it bounce/animate and export that to a little gif or whatever.