I increase my object anti alaise.  It works great.  It even smoothes out shadow edges, grainy clouds, trees, water, and terrains.  I find a problem area.  Then select a sample of that area to render with different object anti alaise settings.  I try to find a balance between render time and quality.  I usually use 12 - 24 for min & max and 100% for quality.  I use soft for the type of object anti alaising.