Fresnel (node) is the same as facing factor (pronounced frenell/fray-nel btw :)), except abide to laws of physics, where the governing factor is (real factor of) material index of refraction. Fresnel (mode) in the layer weight node is supposed to be a 0-1 normalized value of fresnel values, but I don’t know the range or how its computed.
Fresnel (both the node and layer weight mode) currently seem to bug out badly with Transparent Shader, and you’ll have to approximate using Layer Weight in Facing mode. For dielectric reflections (plastics, glass, topcoats etc) I pretty much always use Fresnel (node), maybe at high values to get a more solid effect, and then multiplying with <1 value to bring down the reflectivity if I need to.
True, “specularity” used to be just fake reflection of light sources. Now, specularity and reflection is the same thing. However, it would be extremely useful to have access to a isotropic/anisotropic specular “ramp shader” which doesn’t deal at all with real reflections.
Cycles have a non activated Phong shading as a specular distribution model, but I’ve never tried it. Does this reflect as well? If not, does it have limitations to what kind of light sources/emitter will be accounted for in shading? Hell, even with use restrictions this would be extremely usable as a builtin shader, if only to add to other shading effects (iridescence being a perfect example, for when the real thing isn’t simulated at all).