Cube, grid, displace, duplivert.
Cycles: 1000 passes, 3:44:00
Touched up with GIMP to remove a few fireflies 
Simple, but still awesome. I can’t tell if you applied focal blur, but that could be a nice touch as well.
I did not use any depth of field here. Just some fast gaussian blur to add a slight glow to the yellow cubes and some gamma correction. I used a material pass to isolate the glowing cubes, I also used that to add the glowing cubes to themselves using a mix node to help them stand out a bit more. Also threw in somewhat heavy AO.