When I was on Mac and in the earliest versions of atom, I suffered through the slow startup time and keystroke lag for the ease of customization (JS/coffee, JSON/CSON; vs custom DSL, C, Python or whatever). Altogether, I'm not very opinionated about text editors, so the pros and cons were pretty negligible. Upon switching to Linux, the performance were gone. I don't know if it was because I'd been using too old of a version on Mac or if OS X just has a latency penalty for using web views.