The 4K Retina display makes a big difference when using apps that take up a lot of real estate. I do a lot of digital painting work on Autodesk Sketchbook Pro and other apps where having the sharpest resolution is crucial.
We do a fair amount of video editing as well, and processing video in After Effects or Premiere is blazing fast. I like the new keyboard too, it feels similar to the one on my MacBook Pro, very comfortable and fast.