um, pardon, but isn't that a factor of the reflection node? that is, isn't that one of the settings?  i remember my first experiments with reflection (just a plain floor- just wanted the figure, not an environment) had a blurred reflection.  not very fine, but the samples were low.  i suspect that reflections will have the same sampling issues that ambient occlusion and raytraced shadows have, but you could give it a try.