I am trying out Lightroom CC now since I am considering owning newer Nikon D750 and I need a RAW processor.
To this day I was happily using Lightroom 4.
I have noticed several issues with Lightroom CC:
1. it is really lagging
2. On some images (not many) it produces weird artifacts that look like dirt instead of noise, when looking at RAW images coming from D800e. Openning the same RAW image in Lightroom 4 does NOT produce these artifacts.