I am also running OSX 10.12.1with the K65. It was driving me crazy until I finally plugged in my mac keyboard again. The shift and ctrl work, say if you want to capitalize a letter while your typing...the part that is not working is when for example when you hold down shift when using finder and try to select multiple files. I believe it says right on the ckb issues that the modifier keys are not working but until now I didn't really understand what that meant. I love this keyboard. I swap out a Windows 10 laptop and my mac laptop quite a bit depending on which machine I need to use. It wasn't until a week ago or so where I was trying to do some editing in LightRoom and it was driving me crazy I couldn't select multiple images. Now that I know what is going on, it really does make this not really usable now running on Sierra.
Corsair, if you read these, I was about to buy a second keyboard but this sort of incompatibility going to put my purchase on pause for now.
