Nightlight is asking me to give up the comfort of Emacs: so what does it get me?
Perhaps nothing. But for me it would give me the fact that it's not Emacs.
I know that Emacs is considered the one and true way to do lisp, specially common lisp, but, for me, it's the reason I haven't started to do anything in that language.
Different people, different needs. It might cater someone else's needs.
And Emacs isn't the only way to do CL, it's just got really good support for all lisps: Paredit and SLIME are still some of the extensions against which all others are judged, with most lisps having a SLIME equivalent mode, give or take.
But what's so bad about Emacs?
The time you have to devote to learn it.
I get that when you are used to it and use it you get that time back, but I haven't had a job where I could use that, and when I had time I was more of a vi person.
On can go up so many learning cliffs until he gets tired of that and just yearns for interfaces that are similar to the ones already known or so easy that no learning is necessary to start using them.