I primarily use Jupyter Lab. I have some frustrations but I generally like being able to manage multiple kernels from one notebook, having multiple views into one notebook, having context-sensitive help, and having some of the other features that were only in Lab.

That being said, I'm glad they've switched course and continue to work on Notebook once it became clear some people preferred it to Lab. With some of the added features and the ability to switch between Lab and Notebook more easily, I may give Notebook another try.