The performance took a huge hit. It now takes about 4 times as long to compile, and my laptop is about to burst into flames as it's running. Getting about 9 FPS. So the scene is a bit dark because I'm only using 50 photons.
One other minor improvement I did was to also add specular highlight as an extra step after photon gathering (similar to what I did with shadow). This shows up as the white hotspot on the glass sphere.
Results looks nice though. Here it is!