I could not turn off mouse acceleration, which was a deal-breaker for me.
Actually not Wayland's fault if I remember correctly, something about libinput changing it's format, and my window manager wasn't compatible with it yet. After trying for several hours I found a bug report (can't find it right now). The Devs thought it was a minor issue, but for me it was huge so I decided I'll wait another year.
I must say, Wayland was smoooooth, didn't even experience X as slow until I tried Wayland.