I had just copy pasted over 2200000 chars , made up of 21 lines.
Atom take it like a champ , only stall a bit , can still select word , enter new line , cut , delete. I am amazed.
I tried the same to ST3 and it just stop responding and i had to force closed.
Proof included , try for your self and see it works.
If thats then , the long standing argument of Stuffs built with purely Web technologies (ATOM) can’t match performance of Native apps \ is no longer true.