Oh, interesting. I had that checked. After unchecking it, the single frame render directly in Poser did use the GPU. Have not tested the multiframe methods yet.

That's kind of annoying, because I do still use Firefly as well and it improves performance there. It would be better if Superfly just ignored that setting, so I don't have to go into the general preferences each time I switch (which I am guaranteed to forget).