[headwayoldest]

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

[tw04]

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.

[pbreit]

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

[patzal]

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

[marcosscriven]

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.