Changing site has nothing to do with getting them to accept dazzle For sound. It's just a pain in the rear end altogether, like said get the newest drivers and that sometimes gets it.
Most of the time you have to get extra hardware so it picks up the sound but i'm not to fussed, A good microphone is all you need and you can do commentary to.
and is over-all just a better site.
Better depends on what you want,
Want HD streaming, sure go for justin.tv but expect huge bandwidth use.
For lots less bandwidth use ustream is the way to go and is my personal favourite.