The main problem it solves is that emacs is a tiling window manager (in a loose, non X-specific sense), so if you spend the majority of your time in emacs it gets quite annoying that you're having to use two different paradigms to manage windows: one for managing emacs "windows" and the "buffers" that they "visit" and one for managing X windows, of which emacs itself is one. EXWM makes X windows behave (mostly) as if they are emacs buffers, so you can use the same powerful tools to manage them.
As an example, I use ivy (https://github.com/abo-abo/swiper) so for switching between buffers I get a nice incremental fuzzy-matched buffer list. With EXWM that same buffer list also contains my web browser and other X applications.
I've written a toy window manager so I have some sense for what making a real one would entail. I've been using emacs for 20 years or so, so have some insight into that. I am in awe at the dedication and attention to detail it must have taken to turn EXWM from a crazy idea into a solid WM that is completely usable as a daily driver.
I can imagine that EXWM eliminates the need for SUPER, which for me would free a modifier pair for a useful LVL3.
I currently have a super on both sides and need to shift super in order to get level 3. Some pedals would be nice.
[1]: https://github.com/emacs-helm/helm
[2]: https://github.com/abo-abo/swiper
[3]: https://www.emacswiki.org/emacs/WindMove
[4]: https://github.com/abo-abo/ace-window
[5]: https://github.com/Bad-ptr/persp-mode.el
[6]: winner-mode, one of my favorite things. https://www.emacswiki.org/emacs/WinnerMode
It’s not entirely clear to me from the page what features set it apart. I guess part is familiar keybindings if you’re an emacs user?
The screenshots look like it does some tiling, is that a good experience? I use i3 so would be curious to know how this would compare.