Atom is noticeably slow for me on a modern rMBP, too. I'm using version 1.1.0. It used to not even let me open anything but the smallest files. I think the li

Atom is noticeably slow for me on a modern rMBP, too. I'm using version 1.1.0. It used to not even let me open anything but the smallest files. I think the limit was a mere 2 MB! I do not get that denial any longer but it still feels slow especially for larger files. Sometimes I have to open 500 MB text files. Atom cannot handle them, while they open nearly instantly using MacVim. So in these modern days I use MacVim more than I use Atom.