It doesn't open instantly on my work (Windows) desktop. But then I don't care as I generally open it and leave it open all day.

Same with Spacemacs. because of the way processes are more expensive on Windows, Emacs/Spacemacs is many order of magnitude slower than it is on *nix (the other places I use it). I tolerate it as I can't live without magit and Org and other staples.

I find the crappy Slack app (another Electron app) is also slow to open, load and update. So much so, I prefer to use their web client in a browser.

Anecdotal, also, but that's two Electron apps which are sluggish on fairly recent (3 years) hardware.