Quote - Now I haven't read any of the documentation, including the new features list, but.....

Agents Smiths marbles picture seems to have caustics.    Can this be true, or does it just look like caustics and it's actually just refraction?

how could it be refraction? what is 'just refraction'? the spherical distortion you see through the glass marbles, yes, that's refraction, but the brightening spot nearby under those same spheres, I don't think that's possible other than through some form of caustics, faked or precise, or through some post work (easy enough in a case like this to lighten up an elliptical shape).