I'm having a hard time adjusting to the Project Panel on the right (and, at least for me, hidden by default) - seems like they're trying to bury the concept of a 'file'?
It's certainly interesting though, and I'll give it some time - the post says "It feels more natural once you've spent a little time with it"
I think it's more that you don't need to look at the actual tree structure all that often, especially when most codebases follow logical and conventionalised structures you remember these structures and can use Command-P to search for files individually to open and the tree structure becomes something you peek at infrequently to ensure that everything is going in it's right place.
You can move it to the other side panel by right clicking the Project icon that toggles the view.