It is called Mellel, which works well with Scrivener.
What is Mellel? It is a word processor.
So what? Well, it is stable. That is something I appreciate in any application.
It is also an evolving exercise.
Though it does have some problems.... (I will need to go to my other work horses when I need an index, or to edit large swaths of text)
That said, it is stable... did I mention that? And Neo is not as stable as this sucker. And I-Works is not as stable either
Now word processors are like wine, and we may not agree fully, but for banging out first and second drafts, I like it. I actually bought it, and I am using right now at Lion's Coffee House... while listening to San on the Rachel Madow show.
Here is a link.... (and if you are doing academic writing it MIGHT be the ticket since it also works with bookends)
http://www.redlers.com/