I'm very pro post-work.  To me, photoshop is just another tool in my digital toolbox.  As long as it does not degrade the finished render.  One thing I use it most for are background.  There are times when I just don't have the actual content to produce the effect I want or to place my subject in the location I want.  In that case, I'll readily and willingly use whatever I need to to complete the job.  

     An analogy would be a ceiling patching job I recently started.  Giant hole in my plaster & lathe bedroom ceiling (involved both of my feet and a too-weak attic floor).  Cleaned up the jagged edged and pulled out the stray pieces of lathe, cut a giant section of drywall, screwed it to the ceiling joists, and then covered over that with drywall mud which I had to smooth with a wooden bed-slat since they don't make taping knives larger than the hole.  The correct way to do the job would be to have put up new lathe to fill the hole and then bring it up to level with successive layers of ever-thinning plaster and then hand-smooth it to blend with the ceiling.  Even doing it with drywall I didn't use the "correct" tools.  I merely did and used what got the job done.  Still needs some finishing work; but then I still have renders on my hdd from five months ago that need "finished."  Avoiding procrastination is not one of my strong suits.