With all the people complaining about Atom performance, I cannot confirm this. Switched from Sublime Text about two years ago and never had speed/snappiness issues. If anything Atom does quite well with gigantic files.
On a 500 line file when I start adding multiple cursors, after the 5th or so It starts taking multiple seconds just to select the next. This was in December, so a recent version. I can't work like this.