On X11, when I click launch any application, I can see the application starting thanks to an animation in the Task Manager (the icon of the app has a little circle revolving around it) before the window of the appliaction is displayed. On Wayland, there is none. Really minor bug, but "needed" for visual parity between X11 and Wayland, I think.
Yeah, there's no support for startup notifications on Wayland yet.
*** This bug has been marked as a duplicate of bug 402903 ***