But emacs remains replete with bugs, the performance leaves a great deal to be desired, the UI locks up if you update your packages because the whole thing is single-threaded, and emacs lisp (the language) quite frankly sucks, a lot.
Lem is not very mature and has a lot of sharp edges but already in this state I can see that it will eclipse emacs if it continues its current trajectory.
Still very Lem-curious, though!
Also, Elisp isn't really that bad. Well, sure, Common Lisp of course is a lot nicer language, and of course, not having any good concurrency story doesn't add any points, still, Elisp isn't so horrendous.
That being said, I do really hope Lem would get traction, and people start building plugins for it. Alas, realistically I'm not sure how feasible that would be. Replicating anything like Org-mode, with tons of extensions may take many years. Lispers however are known for their tenacity and ingenuity, who knows, maybe it wouldn't take too long.
I use Emacs every day. It is my editor and in general tool of choice. However, the longer the concurrency story is not improved, the more advantages do other projects accumulate, because this concurrency thing is part of everything. Even VSCode seems to be better at concurrency. What a shame.
I think the only way in Emacs to properly use multiple cores for speedup is to start external processes. Sometimes that is a natural thing to do. But one also needs to process the result of an external process. Say for example a huge git diff in a magit buffer. All that stuff needs to be rendered/fontified. Editor locks up. That's just really bad. And people discuss workarounds all the time, writing code with these limitations in mind, meaning, that this makes code more complex everywhere.