Another thing to note on reflection/refraction blur is your environment shading rate, having this at default/1 may not be low enough to get rid of the grain with high AA or blur samples alone. Try lowering this in the shader or master tab...a warning though, this will increase render time, but with a well balanced setting of samples/aa/etc you could be better quality at a faster rendertime, its just going to take some experimenting.
Above is an example of Environment Shading rate differences. The object is refracting, but quality of env shade rate effects refl pretty much the same. The left render is set to 1 (rough/default), the right is set to .1 (highQ). This alone is just refraction, so imagine if this had the default env shade rate of 1, and refract blur, it would take a bit of tweaking.
The second image shows an extreme example of low reflection blur samples (only 5!) but maxed out importance samples, 100, and .01 env shading rate with 1024AA samples. Despite the uber low refl blur samples, the grain is not horrible, but of coarse, this is an extremely unbalanced render quality scenario, but it shows that its not all about high blur samples. It would be nice is shaders had independant env shading rates, not just the norm shading rate over ride.
Message edited by ambassador on 1/3/2013 - 3:56 PM