Thanks to the viewing options available in today’s image editors, it’s easy to view images at extremely high magnification. Many people do that, just because they can. I ‘ve found, in my own work as well as others, that it can cause as many problems as it solves. For example, many people photograph flat detailed surfaces every time they buy a new lens, and peek carefully at the results. With today’s high-resolution cameras, the slightest flaw in focusing or camera/subject alignment can cause visible flaws in the image. In that case, pixel peeping can result in perfectly good lenses being returned as defective.
Even if the test setup is perfect, many lenses will show visible defects under high magnification, defects that will have no effect on actual photography (as opposed to testing). Those lenses often get returned as well.
When the testing is over and the gear is put to work, pixel-peeping can cause lots of image editing that’s marginally visible. Is that good or bad? It all depends.
When it comes visibility of imperfections in images, two things are at play. The first relates to the viewer: is the technical flaw observable? That depends heavily on print size. I normally print in three sizes: 17×22 inches, 24×30 inches, and 44×66 inches. Very rarely I will encounter a customer who — be still, my heart — wants a 60×60 print, which I can’t do at home, but am delighted to go to a local printer for. Detail visibility is also dependent on the medium: baryta papers are very sharp, matte finish much less so, and the canvas that I use for 60×60 prints even less so. I know that conventional wisdom is that people back up from big prints so that the size/detail relationship is mitigated, but that has not been my personal experience, nor my experience when watching people view my work in a gallery: they get just about as close to the smaller prints as the larger ones, although they also back up from the larger ones to take in the whole effect.
So how picky you need to be depends on the intended size of the image.
The second thing is the artist’s attitude towards imperfections. There are some people who, once they’ve seen a tiny flaw in one of their images, won’t rest until it’s fixed, regardless of whether any other viewer of the image could reasonably be expected to see it. There are others who are less tightly wound.
For myself, it comes down to what I’m going to do with the picture. If I’m going to sell or exhibit it, there’s no flaw too small for my to attempt to excise. One of the things that’s great about making art is that you can take all the time you want to fiz things that are important to you, regardless if anyone else will ever notice. For other uses, I am more relaxed.