I was actually pleasantly surprised by Atom's performance. It used to be remarkably slower than VS Code...like dramatically so. Now, it seems to be breathing down VS Code's neck, in terms of performance. (Both are the chubby kids huffing and puffing along at the back of the pack while being lapped by the other contenders, of course, but they're trying.)
That's interesting to hear, because I've tried Atom three times now and the biggest deal-breaker every single time has been performance.
Around the first release, there was noticeable lag as I typed. About a year later, tabbing through find results was just absurdly slow. More recently, opening a multi-megabyte JSON file with syntax highlighting was an inexcusably painful experience.
I really, really want to use and support Atom, but the performance compared to Sublime has just been atrocious (in my experience).
Oh, it's still slow. Pathologically so in some cases. But, so is VS Code. But, Atom's speed has become manageable in recent versions. I rarely find myself unable to work with a big file in Atom. For code, I rarely see files bigger than a few thousand lines (and never produce files that large myself), and Atom handles them OK (not great, but acceptable, given the other benefits of the tool). VS Code is still better, and of course, vim smokes them both. But, there are trade offs, and Atom has a lot of cool features.
I wouldn't use it for really large files, however. It really shows its ass in those cases (as the XML file test here shows).
I don't notice typing lag, anymore. Just now I opened it up and tried to get ahead of it by slamming flat hands on keyboard, but it kept up fine.
My current performance complaints are: startup time, big files (especially big files with highlighting), selecting large blocks of text (spanning more than a screen), and probably some other things I can't think of right now. Some of the plugins are buggy and prone to screwing up more than just the thing they're supposed to changing, but that's not performance-related. Just immature code that's expected of new-ish projects.
