I have ben working on an animation using a modified human figure as well as the stock "cat"
I set a scene in Carrara and do short animations in Poser, then Tanspose them in. It works as advertised. Because of the nature of the import, the figures always come in under ground, but that's easily adjusted. The texture maps come right along as well as the Poser light setup so you need to delete/adjust them to your scene.
So far, I have not had two animated figures operating at the same time in the Carrara timeline, but the individual moves come along Ok.
I hope this answers some of your questions.(Mac OS 10.3.3, Dual 1GHz G4)