I believe you must have some very specific driver issues or something, because for me Photoshop CS6's performance was equal to CS5, and CC's performance actually went up a little as compared to CS6.
Could you be specific about exactly what you're testing and what performance you're seeing?
we work on very large psd and psb files. in the past it would take about 1 minute per gb to open a file and now it takes 3 times as long to open the file.
Also we notice that the efficiency indicator at the bottom goes to 5% many times. After the large file opens, any time we try to do anything it lags terrible, when trying to do anything. We updated our video drivers, but not sure what else to look at.
That sounds like you might be running the 32 bit app by mistake.
I just went around and checked everyone's computer and they are all running the 64bit version.