The default color ramp node in Blender is indeed a very useful node whenever you need to modify range of some color values. However, when creating some versatile node setups, you might be faced with the lack of inputs for the ramp control points. And there is the time to create your custom color ramp node with control inputs.
Lighting your scene with a HDRI (HDR) environment map is a great method how to improve quality of your renders. Not only that it provides realistic reflections for glossy materials, but also creates colored lights and shadows in the most realistic way since every pixel of the environment map actually stands for a light source illuminating the scene.
PBR (Physically Based Rendering) seems to be the standard for photorealistic rendering in these days. All major rendering and texturing packages like 3D-Coat, Substance Painter or Marmoset already have this lighting model implemented. Blender is going to include a real-time PBR viewport in version 2.8. However, no need to wait for the new release, thanks to the Cycles Render, we can already create a dedicated node setup for the PBR shader. We can also use this shader for rendering material maps baked in other programs that already works on the PBR basis.
Exposure value (EV) is indeed essential for every photographer and computer artist. In Blender there is an exposure slider in Color Management allowing us to edit the overall exposure (in EV stops) of the output viewport or render. However, what if we wanted to edit exposure of certain material map in the node editor? Such node is still missing in Blender (2.78), but we can easily create a custom group node for that purpose.
In the current version, Blender contains decomposition nodes only for HSV and RGB color models, but still missing nodes for HSL color model. Since I find the HSL model very useful for color manipulations, especially its lightness value, I've created both Separate HSL and Combine HSL nodes, which enables me to modify each part of the HSL model.
Just a few days ago, a new version 4.7.9 of the Firestorm viewer has been released. Since it brings a few of really neat features, like avatar rendering complexity controls, it still doesn't fix some of the older issues. So, let me summarize the issues I will try to tweak...