Quote - You'll notice it once you let it go for a bit.  Where I've noticed the improvement is in the total number of passes it takes to get to where I consider my render to be done.  The best comparison I could come up for it was one I gave my wife.  It's like having a big black spot on a white wall that you want to paint over.  The long pre-refine brush way was to paint the whole wall til the black spot was gone.  Sometimes it took 10 coats some times it took 50; but, eventually the whole wall was painted so many times that the black spot is not visible.  Takes forever to paint an entire wall 50 times.  The post-refine brush method I use is to paint JUST the black spot(noise in the render, hot pixels, grainy shadows, etc) 10 times and the rest of the wall once or twice until the color is blended.  Both give the same result yet the 2nd way is less labor intensive and quicker.  My refine brush work flow is like this.  I set use it on all hair plus lips and eyes.  When those clear up, I use it on the entire face and usually any metal in the scene.  Then I use it on all shadows til they clear up.  Then I take the refine brush off altogether and let it run on the whole render for a couple hundred passes.  Doing it the refine brush way I've been using cleared up a render at like 450 passes when it took like 2200 the first time I did it with no refine brush at all.

 

Ahhh, it might be that I'm not giving it enough passes then.  I primarily use reality for animation, so I don't usually let it render any one frame very long, else I'd never get anything done.  The current set is limited to 125 samples.  I put a refine brush over all of the exposed skin on the second frame so that I could compare with the first frame.  There didn't seem to be any noticable difference between the frame with and the frame without.