Atom is great in many ways, and I personally don't have any major complaints about speed, but it disappoints me in lots of little ways. For example, on two different machines, when I upgraded to 1.7.0, Atom failed to reopen my open tabs - they all became 'untitled'. And a couple of them were unsaved (my fault, of course, but I hadn't ever been burned by Sublime doing the same drill).
Also: Doesn't ask me to save my unsaved files when I close the editor. Sublime Text called this feature "hotexit", but in Atom there's no way to disable it.
it starts with the speed, atom is clunky and slow. If I do not have any other alternative them Atom is good enough, but geany and vscode are way way better than atom. I'd rather do all fancy plugin stuff of atom using python and use geany than use Atom because of its slow speed. I wonder why anyone isn't doing anything for that considering github is the company being atom and that vscode and atom both are based on electron yet vscode is so damn faster than atom