The current docs don't make it clear why I might choose Atom over Sublime for coding, but it looks like an interesting platform for building all sorts of rich text editors with UIs targeted toward different kinds of writing - if it's as extensible as they claim, I can imagine an extension that turns it into iAWriter, another extension that turns it into a GTD task manager, another to turn it into a native blogging client app... building from there, more complex word processing might be possible.

If this just stays inside the coding community, it will likely be competitive but not universal, but if it can be built to target non-coders, it could set a new standard.