Most gamedev studios create a lowpoly mesh in a polygon modeler with uv-maps and transfer it to ZBrush for sculpting.
And this works perfectly now with GoZ.

@Frank_G:
I'm really not sure it's the more used way !
Look at UT3 models: they start from high model , and make low poly after : you have the bets results like that.
You make the cage fro mthe high polygon.

Starting from low poly is good when you want to add surface details only.

Well i really prefer a lot ot be totally free in terms of creation :
Create hight model from ground , in 3D Coat add freely any 3D parts models in Voxel Trre( sort of 3D layers) , add details to them as i want.
Once High 3D model is done, ok : make retopo to have a very precise low poly model, to bake noral map.
With retopo you avoid lot of normal map seems ?

OR perhaps i'm wrong, and i've not see enought workflow from other people ?
But i'm not sure you can do as good results starting from low poly version ?

In fact if you look at forums on Polycount, game artisans or other forums, look at Next Gen characters thread work in progress (Dominance War 4 thread or any otehr challenge) :
you'll see that people sculpt high poly version, than make low poly version at the end !
That's today workflow i think ! (perhaps i'm wrong ??)