Maybe on a slow pc, but with Atom on my macbook pro I have no performance issues at all period. I code 8+ hours a day (for many years), and no my fan is not spinning all the time because of Atom. I have 16Gb ram, have multiple apps open at the same time, Chrome with 30+ tabs, listen music via youtube, etc..
I was a long time Sublime user, but the $70 they're asking is really way too much with so many great open source alternatives today. Would they at least divide the $70 to all the package writers that actually make Sublime a great editor I might be willing to spend it, but unfortunately they want all the money for themselves..
Switched to Atom a while ago, I gained (some really great) features and finally got rid of the trial pop-up.