I have heard of it but haven't read up. I think it's great that someone is stepping up to address the issue. Interesting that both the authors listed in the JEP work for Red Hat.

Shenandoah is unlikely to see the light of production release until Java 10. I ran a very early piece on this - http://www.jclarity.com/2014/03/12/shenandoah-experiment-1-w... - really glad to see more experiments in this space. I'll add that G1 from Java 8u5 onwards is pretty darn good out of the box.