"Correct me if I am wrong, but XStream is mostly an animation integration, much more than a rendering companion.  Most amateur artists who are using Vue, are going to be using it for stills.  They don't really need XStream."

Well, I'll tell you what - I don't know much about the Poser part of Vue 6 xStream, but I think I read something about poses with MT's not being imported properly?

In any event, as a Lightwave 9 user, I've asked  in other forums about Vue 6 xStream, and it is by no means limited to animations. It's my understanding that xStream opens up within the app, and gives the target app access to everything  Vue 6 has to offer, i.e., terrains, procedural mats, atmospheres, .vob files, plants...everything, plus the option to use the Vue camera and lights, or the host app's camera and lights, or any combination, plus being able to combine them in animations.
I'm not using  it yet, but I will be getting it, hopefully soon, 'cause it looks entirely too good to pass up. :)