I've tried switching to Atom several times, but performance always brings me back: Sublime can edit a several-megabyte file with no stress, Atom becomes unusable; I can bash keys in Sublime and they instantly appear on the screen, there's an almost-noticeable-but-wait-is-it-even-really-there-yes-I-think-it-is delay on Atom. Also, vim mode isn't as robust as vintage mode (`ci"` to change the stuff inside of quotes, in particular, doesn't work in Atom).

I really hope whatever javascript/html/css framework they've set up has a lot of room for performance improvements. I'd much rather be using something open source based on these technologies (which, for me at least, would make the editor much more hackable).