Like many others, I've been using Reflux because it seems to be the easiest to understand and to work with by reducing the surface area of concepts you need to understand to just:

1) actions

2) stores.

In Reflux, a store is effectively just a variable you want your component(s) to be able to access and an action is a function that tells the store what to change about its state. For instance, I might have a CurrentUser store that tracks who the current user is and notifies my Profile component when that changes. I might also have a switchUser action that tells CurrentUser to change its state to user #30. That's all you need to understand to use Reflux.

It's certainly interesting to have data fetching baked into Marty, but it also introduces so many concepts. I think it'd be really helpful for people coming from other libraries if you had a big glossary that says what each thing is and why you felt a need to include it. What's a Marty constant and why is it different than an action creator? What purpose does the dispatcher serve? etc.

You'd have a better time recruiting and training new users with a diagram that shows how all these concepts fit together and why you need so many of them.