DS Reality is doing well, and Carrara Reality should do at least as well.

As Paolo says, it's just another rendering option....if someone is totally happy with
Carrara renders they probably won't go for it, but most seem to think that Lux does a better job at realistic rendering, and Reality/Lux is easier to use than Lux. 

According to Paolo at the DAZ forum  Carrara Reality will have even more support for Carrara shaders than those in DS. 

For ~$100 sounds like a winner.