The biggest thing I can think of is that X11 is more flexible when it comes to specifying custom resolutions; which some people use to output 240p on CRT TVs for emulation. AFAIK, there is currently no real equivalent for xrandr on any Wayland compositor.
I’ve also noticed that Grsync’s password prompt is broken on Wayland. Thankfully, it has a feature that lets you preview the command it’s about to run, so that you can copy and paste it into a terminal.
Being a KDE user on EndeavourOS, I use Wayland everyday. I switched over a few years ago for Waydroid, but now X11 isn’t even an option for me with the current release of KDE.
I wouldn’t want that. I’m fairly content with the fact that no random apps can grab my keystrokes unless that specific app is focused. From what I heard, for most people the only global keybind they want is muting their microphone. You can implement that yourself with absolutely no trouble, it will usually be the first example in the global keybinds configuration docs for pretty much any compositor. People who don’t want to deal with writing configs can use KDE where you have a GUI to configure the same thing.