tl;dr: If you're a Jupyter notebook user, you should go install JupyterLab right now and play around with it.
I'm writing this post in JupyterLab, which I just installed on a second computer this morning after checking out this video yesterday afternoon.
Why do I think so? Since beginning to learn about data science tools a few years ago, I've always loved Pytyon more than R. Coming from a software development background, it's probably natural that I'd gravitate toward the environment with a general purpose programming language and an awesome command line REPL environment baked in. There's at least a 75% chance that if I were a statistician I'd have chosen R instead. And by the way, 75% is a made up number -- as I said, I'm no statistcian!
At the same time, however, one of the tools I always wished Python had was an awesome integrated environment like RStudio, where you could have a terminal going, and online help, and a notebook.
With the installation of JupyterLab this morning, I stopped wishing Python had something as cool as RStudio, because Python has something cooler than RStudio, and I'm typing in it now...
Here's how it looks: