Kelvin in MT says:
The new version of Lightroom cc has a left/right panel for comparative views, making matching color and exposure unbelievably great! If you’re shooting a bracketed sequence with flash and ambient frames, color matching is considerably easier than ever before. It can also be used to match all the flash frames, for instance, to each other, using one frame as the reference, and matching the rest to it. It’s a fantastic improvement!
The tutorial above illustrates what Kelvin is referring to.