I am running a mid 2013 macbook pro with 16 GB ram and 2.7 i7 chip. I was using LR CC to process a shoot and after building full size previews and processing images, I have to wait several seconds for the final settings to take effect each time I toggle from one image to another. I have even rebuilt all previews and I still have the same issue. Why does LR have to load new previews... especially if I have not added any edits to the image once the preview has been made? If I go to the beginning of the gallery after previewing each image in the folder, it has to reload the settings again! I was hoping that this machine would chew threw previews instantly ... as my 2007 mac pro does so far more effectively.
In the Catalog Settings dialog, check the settings under the "file handling tab".
In the Preferences dialog, "file handling" tab, check the Raw Cache settings.
In the Performance tab, see if changing the GPU setting makes a difference.