The subdivs value beneath the refl glossi-
ness controls the smoothness of the blurry reflections. Change it to 20 and render. The result is much smoother.
Note that 8 subdivs means 8x8=64 sam-
ples, 20 subdivs means 20x20=400 samples. Doubling the subdivs will take +-4 times longer to render!
Make sure you have the AA sampler at
adaptive QMC when using high subdivs
values! If you want to use adaptive subdivi-
sion AA, you can get away with much lower
subdivs values (3 to 10). The adaptive AA
smooths outs much of the noise from
the low subdivs. If you have many blurry
reflections in the scene, adaptive QMC will
always be faster.