I'm curious about your lighting setups - seems like Mental Ray renders very dark unless I put an exposure
node on the camera, regardless of soft, ibl, or whatever. Without exposure on camera, when using
a spot (with attenuation, which I know will diminish the power), I generally have to turn up the
intensity to 200-1000 - just curious if this is normal. My models are all relatively to scale (10cm/unit).

Great renders - the updated sss seems much more powerful. One other question - is diffuse+SSS like an
additional 'scale' value?

@ second question: Yes, it's a multiplier or tint for the SSS and diffuse components. It is named "overall multiplier" in the original SkinSSS, I though I'd rename it so it's more clear that it doesn't affect anything else.

its ok, i had values of 6000 or higher for physical lights, but i render without exposure shader the most time. physical values are completely different to light without falloff and intensitys of one like in old school setups. physical sky shader for example and sun intensity values of 100 for ibl are normal settings.