Best result so far. 128-1024 spp, 12mins 30secs. Specularities are still a bit bigger.

Looks like I got the intensity of the reflective sphere right [except probably multiple scattering] but I am still double counting the specular light contribution.

Finally something! This is my first attempt to render after reading the Eric Veach for days. The glossy sphere seems a bit dark and refractive sphere seems to be too bright. Render Time: 7m 40s on 1 thread, 16-256 spp. No explicit absorption probability or limits on ray bounces - unbiased, MIS path tracing.