For the most part, leading authorities condemn shoulder holsters. Their reasons are numerous, but the main objection is comfort. There is no question that shoulder holsters are not for everyone.
Many shoulder holster designs are uncomfortable, while others are probably too complicated for the average user. They may require too much attention in order to get the design to fit properly.
My personal opinion is that wearing a shoulder holster is much like wearing a light backpack or book bag. There are backpacks that can be tiring in very short order and there are those that work well, even with moderately heavy loads, for far longer. The key seems to be in getting everything in tune with your body style and profile. Getting any shoulder holster properly fitted requires patience, time, and trial and error. A full-length mirror also helps.
You have to watch and examine how the holster hangs along your sides as well as how badly it prints once you put on a covering garment. Go through a series of movements and then go back to the mirror and see how well everything stays in place or where it moves to, so you can figure out further adjustments.