I am in process of switching from emacs to neovim atm (doom evil user before). Whatever I do in emacs (emacs28, jit-compilation, M1) I still experience some UI lags l cannot get with profiler. I suspect slow lsp interface and suboptimal caching/gc. At some point I've tried neovim and was just surprised by how fast it feels.

Company mode is the big offender for me, it handles very large completion lists poorly. I'm not yet fully satisfied with the latency situation in my emacs config, but for me there is no going back. Evil mode let me keep almost all of the muscle memory I ever learned in vim/neovim, and the rest of the emacs ecosystem more than makes up for the latency issues in my opinion.

Corfu might be worth a look, as a lighter weight alternative to company mode: https://kristofferbalintona.me/posts/corfu-kind-icon-and-cor...

And Corfu was written by the same person as this OpenStreetMap Viewer.

I've also experienced some heavy lag immediately after startup - maybe warming up the caches? Had a feeling it gets worse after each package update with compilation.

Long line performance is still a huge problem. Emacs team does an amazing job keeping up, but the age shows itself everywhere. In the end I've realized that org/magit were not life-changing for me, evil-mode it the only thing I care about. :)

Honestly this is a big thing that emacs folks don't value, multi threaded performance.

I don't even use LSP because I have my own ways of browsing source code through emacs. So I go off and tout emacs' amazingness, but then when someone tries it and attempts to use what worked in other editors, it's a slow laggy mess.