Awesome effect!
One thing you could do to improve to accuracy of the reproduction would be to actually sample the scene texture at the lower resolution of the halftone pattern. It looks great but you can also tell that it is kind of rendering on top of the scene when you look at the thin dark shadow details. In real halftones those areas look more like a cluster of the random sphere sizes straddling the border.
One way to do this would be to sample using the ‘mosaicUVs’ function (look in engine content in content browser for some reason that one wasn’t exposed to the search library) where the mosaic size matches the number of dots. The trick to making it work seamlessly is that you will have to get the value of the neighbor pixel cells and also include their distance calculation so they can blend seamlessly. It will be a bit more expensive, about as expensive as an outline post process.