I've been coding plain JavaFX + FXML all week. The Type Safe Builders are a huge improvement when the UI starts to get bigger. I'm refactoring with fx:include and multiple Controllers as is a good FXML practice. However, there are now several awkward pairs of FXML/Controllers that I have to juggle in Scene Builder and IntelliJ.
I mentioned XCode a few days ago. They have a tool called the Storyboard Editor which ties these together. You see your whole app's navigation and can select the individual screens. The IDE also lets you jump in and out of the code supporting the graphical UI constructs. I thought FXML might advance to that point back in 2012, but it hasn't.
TornadoFX isn't WYSIWYG, but the single artifact makes my development time lesser.