It started with video about intentional programming or interfaces. It is a very impressive demo. Then Chris Granger went on to create a demo of his own in 2012 and start a Kickstarter project to support creation of open source ide. What he created is a fun environment, not as ground shattering as we were led to believe, but still great place to have fun while programming. In the end, as his interests moved on, he published everything on github where it still have some development, but I believe it kind of died down for now mostly.
Also, it would be a disservice not to mention large number of plugins available that provide support for most languages and formats.
As a development environment, I can’t say I could use it exclusively, but it is fun to use for occasional project and it does have productivity enhancements. Where I could see it would be useful is in workshop setting where groups are provided training, so instant execution and visibility of variable values would be of most use.