Clasen shares that there's been a lot of work on fixing of dialogs/menus/other-popups for Wayland scrolling, kinetic scrolling now works on Wayland with GTK+, and drag-and-drop under Wayland is comparable to what's offered by X11. Those are items previously already covered on Phoronix and present in GNOME 3.19.4.
Some of the upcoming items on their agenda include initial support for Wacom tablets, a replacement for X11 primary selection, and inside GTK+ the menu positioning code is being reworked.
Matthias also shared a video preview of the work being done on remote Wayland display support (WebM video):
More details via this blog post.