> it is so similar to Java code, that any Java developer can pick it up
Perhaps Java 7, but Apache Groovy doesn't have the lambda syntax from Java 8. Development on Groovy has stagnated -- someone even contributed a fully working Antlr-4 based parser to replace their outdated Antlr-2 based one last year, but it's been sitting in their development repository at Github going nowhere ever since.
We use Groovy at my work in a majority of our projects as well. I love traits and some of the other shortcuts and I don't feel like I'm too far away from Java that I couldn't work in it immediately.
We still love and use Java a lot and they both complement each other very well.