I primarily use CSP on the desktop, the previous UI is gray rather than black/dark so this update is very welcome at least for me. The text is a lot easier to read too, the icons are simpler and less distracting, although for those who just recently started using CSP might have some trouble getting used to the new UI.
IMHO, the new UI isn't that much problematic to get used to especially when you've been using the program for a very long time, mainly because the UI elements are still on the same place as before, only the icons changed. Trust your muscle memory.
So if you are new and confused with the new UI, I highly suggest assigning a shortcut key to the tools and actions you use a lot