For what it's worth, the real scourge with emacs seems to be people's bloaty config files. I have a fairly small .emacs with maybe five packages to load, takes about 1.2 seconds to open (and finish displaying) on my mac, about .2 seconds on my linux workstation. The editor itself actually starts up much quicker, about 110ms on my mac, 40ms on my workstation. Also, generally I use emacs daemon, so I don't really need to start it up at any point.
I don't tend to open files in excess of 100MiB, or do more than about 20k replaces in a file interactively, so I never really notice latency on operations.
I don't care how long my Emacs takes to boot up (currently probably a whole bunch of wall-clock seconds what with all my config files being tangled from Org mode or whatever), since i only start it once every few days or even weeks (when i reboot the kernel, haha i mean host computer, usually).
The importance is that things like 'magit-status be instantaneously snappy to open, which currently leaves a lot to be desired.
Slow emacs start times are very solvable with some smart lisping. Basically, don't '(require)' anything directly, instead make it load lazily when you invoke a particular mode. So set up lots of hooks. Moving your settings into the Customize system lets you do a lot of this for free. After I converted my 10+ year old .emacs into customize and lazy hooks it sped up from roughly 8 to 10 seconds to under a second.
And I also use emacsclient, which make it just instant.
I don't tend to open files in excess of 100MiB, or do more than about 20k replaces in a file interactively, so I never really notice latency on operations.