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.
Not if you want to use KDE on Arch or derivatives.
It is nice that Wayland is more secure, and that’s one of the reasons I started using it before my DE started mandating it. But, it’d be nice if I could keep most of that security, while having the option to enable certain things that are disabled for security by default where I need them.
Going back to X11 and its total lack of security isn’t an ideal option, and I can’t even use my preferred DE with it on my preferred distro.
SonicDE is in the AUR. For people who want continued X11 support for KDE, it looks like this is the project to follow (and vote on in the AUR to promote it to the main packages repos).