I wrote a post about setting up Atom for web development around a year ago:

http://www.developingandstuff.com/2015/04/setting-up-atom-fo...

after using it for around a year.

I think what's more important about Atom's speed is not the speed itself, but the rate at which it increases. Atom was slow 2 years ago, became faster 1 year ago, and today is faster than that. On the other hand, Sublime Text, on a similarly specced computer (of a colleague), today, seems much slower, for example, when doing a project-wide search.