Atom is strange to me, it seems like a less familiar Sublime Text with no real distinguishing features.

The distinguishing feature is it's horribly slow with large files. The performance is an order of magnitude slower than sublime text. And it doesn't auto-save unsaved work if it closes. Both deal breakers for me.

Extremely slow to load, too. Brackets and TextMate load much faster.

unfortunately you are right. Hopefully these issues will be solved soon, I liked the core ideas of atom.

I've used Sublime Text a lot, but moved over to Atom after they moved to the React framework (and hence much faster).

A major 'distinguishing' feature IMO is that it's open source, and very actively under development.

Big files support yet?