I have really noticed a hit in performance with Photoshop CC in Apples latest OS. Before I upgraded to Yosemite, Photoshop was really smooth on my iMac, but since upgrading Photoshop feels really sluggish and when panning around an image or trying to use the lasso tool it's like everything is moving in slow-motion. Is anyone else having this issue? I have had the same issue on two different iMacs. And I'm currently working on the top of the line iMac 5K with 4 HHz i7, 32 GB RAM and AMD Radeon R9 M285X Graphic Card.
At the same time, I have no issues what so ever on my Macbook Pro that I have not yet upgraded to Yosemite. With the old OS Photoshop runs perfectly with no glitches, which puzzles me since that computer in theory should be much slower.
Any help would be really helpful. I have tried the WhiteWindowWorkaround with no success.