Brackets is really neat, it just attempts to be a good editor, it has some unique features like toggling css inline from an html file for example and other jazz.
So Atom isn't something that's really set apart from webkit-based editor, but I don't think that's what's important here. It's the potential the stack offers us.
There's also not as much competition in this area, but it's sorely needed. I feel vim, emacs, textmate, sublime and most the editors are generally closed source or have huge code bases, and they are hampering the process of innovation by creating walled gardens or creating a barrier to entry. With a editor based on web technologies things really open up a lot.
Think about an editor where you can write a feature, pass the tests, and have a hot reload. No compiling, no closed source or plugin system. Just simple coffeescript/javascript some html and css. And bam, you've rewritten your status bar without effecting work in progress. That's something an editor should give us.
I digress, I'm just excited by this.
I really just want something with Emacs' principles that doesn't have as much cruft and runs on the web. Light Table seems to be the best bet so far, but this looks interesting as well.
But to your main point, I would assume this has really really really good github integration...
For one thing though, we can probably expect incredible GitHub integration.