Poser models and objects were originally .obj files anyways made in some other app as Poser doesn't actually support the making of models so there would be no quality loss. However as for the textures, rigging and everything else I am not so sure about.

I recall that Poser has to export a rigged and posed character in .obj for importing into Bryce, a app I used to use a while back and the textures and stuff where all there. However, I have no idea how Maya would handle it. Further more, import features between different apps are different, so an export which may work in one app may not for another.

As for the demo version of Poser, there is one but I think its very old (it was the last time I looked). Anyways, the demo wouldn't support exporting, importing or even saving so it would be of little use (except for playing around with).