Oh, there's a few Poser animators out there...at least 12 of them. And it might make more sense to not call it layers and what it really is; non-linear animation. The whole thrust of NLA is to not require you to keyframe all actions on one timeline. It's like musical scoring; you lay down a fundamental rythym (base layer), then start adding, building on that base. I'm still in the experimental stage myself, but so far it seems that using the layer scheme avoids some of the more common issues in linear animation (like what happens to someone who keyframed a sequence with spline interpolation, tweaked one key eeeeeeever so slightly, and suddenly had a spas dance on their hands). The NLA implementation seems to add the needed spline breaks to prevent this...although I haven't really tried to force the issue to happen. That said, it -does- require you to plan, and break old habits.