Yeah render has IDL problems. IDL does not like transmapped hair at all. Yet there are times you want the hair to cast a dramatic shadow on the face so turning it off in ray tracing to get around the IDL issue is not a long term fix either. Square falloff seems so far to add to the render issues whereas linear fall off seems in limited testing to work a whole bunch better. But lots of variables still to mess with yet

Gary

"Those who lose themselves in a passion lose less than those who lose their passion"