I think Dirt Rider did a write up on them, but I can't find it on-line. From what I remember the benefits are that they don't feel "dead" like a tube and you can have a puncture, or a few punctures and you still have the rest of the balls inflated. I think it was fairly expensive ($100+) and they had a special mounting fixture.
If you absolutely cannot afford to have a flat, the inserts or the balls would make sense, but otherwise an ultra-heavy-duty tube works well. I haven't been able to flatten one yet.