I have another issue where a basic functionality is (at least partly) broken in Photoshop, and Adobe choses not to react or worse yet, simply deny and reject it:
on Mac Retina displays, 100% view is not fully sharp if GPU support is switched on - which is the default - and both image dimensions are odd numbers (like e.g. 4001 x 4001).
The slightly blurry rendering makes assessing critical sharpening impossible, and the only way around is to resize the image to even dimensions.
This might seem an exotic case at first, but if you crop a square image, chances are 50% that you run into it. I have reported the problem to Adobe, but only received the following reply from Chris Cox:
"At 100%, one document pixel is one screen pixel.
At 200%, one document pixel is 4 screen pixels (the way many browsers display images).
You could be seeing a video card driver problem. "
Since I have tested and seen it both on my iMac 5k and on my wife's Macbook Pro, with OS X 10.10 and 10.11. (and different video cards - AMD M9 R290 vs. Intel Iris 5100), the problem is almost for sure within Photoshop.
And even if it were not, Adobe should be highly interested to investigate it - but no further reaction to my subsequent inquiries ... simply disappointing.