I'm sure more people postwork than not.  However, it depends on what kind of postwork you mean.  If you're talking about simple color correction, levels, and maybe a little compositing, then that's extremely common, even among large studios.  If you mean painting over renders, and completely drawing things in photoshop over a figure (like clothes and hair), then I would say that is not as popular today as it was years ago.  The reason is that many elements of 3D today are vastly improved over just 5 years ago.  Things like materials and lighting are rarely in need of paintover improvements, because we now have very high quality render engines, like Luxrender or Octane, available at reasonable prices.  Also, the quality of models available, and their rigging, is far superior to older figures.  Genesis, weight mapping, etc.

I personally only adjust levels or gamma in post nowadays.  All detail I achieve now in the render, and the results I go for are photorealism.  Paintover work rarely looks as photorealistic as what you can achieve from a high end render engine with great textures, detailed realistic models, and physically accurate lighting and materials.

It also would depend on your talents and goals.  Would you prefer to do several hours of prep work before the render, to achieve photorealistic results, or would you rather several hours of postwork to paint in details over a fast render?  It's up to the artist to decide now, and not so much the limitation of the tools.

I took down most of my gallery images, but the one I do have in there is an example of Poser with Octane render.  No postwork at all.

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.