I've been using the importer/exporter, and I love it. The importer has worked beautifully on everything I've tried so far, about twenty or so items in the freebies here at Renderosity. The Exporter is a little more touchy, but also works quite well, at least on my ancient XP 32 bit machine.

A few things I've learned while exporting to Poser:

All objects have to be UV unwrapped even if it doesn't use a UV map. Even a standard cube with a color wouldn't export without a UV map.

I don't know about later versions, but my copy of Poser 7 doesn't handle alpha maps the same way as Blender, so some of it won't translate perfectly. For example, in Blender, it's possible to slap a decal over an object with a .png or .tif with an alpha channel by checking the Use Alpha box in the Image Sampling tab, but in my Poser, I needed to combine a transparency map with the decal image through a blender node, then link it to the Diffuse channel.

All textures assigned to a material must be packed, even the textures that aren't checked, or the export will fail with an error message. "... line 583, in execute image = texture.image"

Materials won't import correctly into Poser, at least in my Poser 7, if they have spaces in their names, like "Wall Material". It has to be something like "Wall_Material".

Some of the values won't be the same in Poser. Diffuse Intensity, for instance, if it's set to .8 in Blender, will be the default of 1.0 in Poser, and it makes a difference.  

Procedural textures won't work. They have to be burned to images and packed.

I've only exported about a half-dozen objects so far, but they've all worked great, bearing in mind the above. I'm extremely pleased with the importer/exporter because it's just doubled the amount of stuff that I can easily bring into blender and because I've been making props for a Poser user, and it's been a pain for both of us working with .obj's.

Thanks again!