Everything you do in Sublime is done instantly. Try opening the command panel (ctrl+shift+p) both in sublime and atom. At least a 300ms difference. Multiple cursors, switching to different panels (I can see the whole pane getting rendered in front of my eyes -- not instant!), even things like loading the list of installable plugins or installing a plugin is far, __far__ faster in sublime, assuming package control, compared to Atom!
Sublime also has this insane feature where no matter how many plugins you have installed, Sublime will still start up in about 200-300 milliseconds, as fast as notepad on Windows and faster than gedit on linux. Atom only goes slower and slower and slower the more plugins you install.
When you're used to an editor that does everything instantly, everything that takes longer than 200ms takes too long.