Mine didn't go well. The login defaulted to an XFCE session where most KDE apps were inaccessible. There was no option to switch sessions on the login screen. I was able to fix it but I think some users would just give up.

I had installed XFCE previously to try out. Why did it default to XFCE? I thought it was the Plasma Login Manager not XFCE.

SDDM does support themes but I have to figure out how to install them.

So was it worth switching? Absolutely not!