I haven't used Carrara but I have given Daz Studio with the Game Developer Kit a try. I'll probably use it for my game characters, the human models really do look excellent. The big problem with character creators like this is their tendency to provide nude models. There can't be many games which need characters with bare feet, and the choice of footwear is pretty limited for example. All in all the models you can export aren't really game-ready.

The Decimator is pretty basic and disappointing, yes it reduces triangle count but it does a pretty messy job with no options for symmetry, keeping quad and things like that which I would have expected. I'm using Softimage for animating anyway so I'll do my poly reduction in there too which is far better.