A good point on the DoF( I guess i like the look of overdone DoF, thats a whole nother issue of mine;) ) ha, Why have 6x subsurf? As in, did you use the smooth button on the mesh?
Your right about your comp, top of the line. Strange it took so long.
I would have to guess(from experience) that the raymir+raytransp were tough on such high OSA, the subsurf just icing on the cake.
Of cours, here I am explaining it, and your probaby already know what it was. Sorry if thats the case
again, nice job
EDIT: wait, you used yafray for this didnt you? ah, now it makes sense…