I still prefer Sublime though, Atom is still too immature, and some packages I need don't exist yet or are far too unstable.
That, and Atom is just far, faaaar too slow at the moment.
I also really miss bracket highlighter, it's a super small tool, but very useful. You could tackle the bracket highlighter plugin, it might even be possible with pure less/css depending on if Atom already has this built-in.
And I miss being able to run a Python REPL in Atom. Python and JS are my main programming languages.
I have already developed a plugin for Atom, I hate the living shit out of Coffeescript, but I like Atom's API. It's a shame that the spacepen API was built in such a way that it's unbearable to write plugins with it in pure js.