i've read the notes (very nicely structured information, i must say) at http://www.users.on.net/~pkinnane/ShaderComparison.html and i'm still curious about how the different products interrelate. If you have, say, HyperReal V3, is it still useful to get the Unimesh Realism Kit? If someone gets the new GI Jill, would a Kit still be helpful? Basically, are the non-texture map features largely the same, and if not, what are the particular features specific to each one (outside Poser version compatibility and uv map specificity)?

If you already have HyperREAL V3, there is not much added benefit getting Unimesh Realism Kit. The Unimesh Kit was developed for new users who had P6, for Mac users, and for existing HyperREAL users who wanted the benefits of the latest P6 workflow (like better main light handling, and the bonus of being able to run the script a second time for a character and only have it update the existing nodes rather than replace the whole node network - essential if you are into modifying the node networks by hand and don't want to loose those changes when you rerun the script). If you get GI Jill, she comes with a HyperREAL'ish node set-up (it has a fake-fake sss, and no enhanced spots). With the clean mat poses, she still looks more realistic after using either HyperREAL or the Unimesh Realism Kit on her - although the "dirty" texturemaps are not compatible with the scripts (since the dirty mat poses use some extra tricks). GI Jill comes with the same alpha (sss, displacement and specular) maps that come with HyperREAL and the Unimesh products. Basically, are the non-texture map features largely the same, and if not, what are the particular features specific to each one (outside Poser version compatibility and uv map specificity)? Mmmm, I'm not completely sure what you are asking here. If you go into the product page of each of the scripts, there is a screenshot of the setup dialog of each script, and a description of what each slider does - so that lists the features.

Thanks so much! This answers all my questions.