It is pretty interesting what a big difference halation makes on the effect of couplers. I was playing with the recent playraw submission (link), and this is filmsim in vkdt, fujifilm 400h and kodak 2393, couplers set to 1 and default amount of halation, and then with halation off:
As we can see, when halation is enabled, couplers have a much more natural looking effect with increased saturation but less of the very obvious haloing around edges with high contrast.