Simple PBR contains mistakes. You should build something based on this tutorial (by the excellent cynicatpro) instead: https://youtu.be/pNiVB7tRG68
I have an updated version of Simple PBR I can post if people are interested.
UPDATE 2, 10/30:
Updated version is here: https://jtheninja.wordpress.com/2015/10/31/simple-pbr-v4/
Now that I’ve gotten a chance to test things out in the Ruined Fountain scene, I can now pass out the much-improved version of Simple PBR:
Simple PBR is now even simpler! It now (properly) uses the albedo/rough/metal model used in many newer renderers and game engines.
It also comes with a cousin, Substance PBR. Substance PBR is just Simple PBR with the roughness squared, this is necessary to match the roughness curve used in Allegorithmic’s Substance tools. (bitmap2material, substance painter, etc). Substance PBR should more or less completely match the Substance pbr_metal_rough viewport shader, so you can just bake map channels, plug them in, and go. (I’ll have a more detail blog post in the coming days on how to work with Substance and Blender)
There is also a third group, Simple PBR Spec. This is like Simple PBR, but uses the spec/gloss model instead of metal/rough.
These groups do not have any tools for texture baking/creation, you still need to make those on your own. You may wish to check out Allegorithmic’s excellent guides on the subject: https://www.allegorithmic.com/pbr-guide