I think it useful to collect fixes and workarounds to Gnome 3.18 on TW here: with most OpenSUSE resources focused on Leap release and possibly KDE / Plasma5 the (not so many) Gnome on TW users may benefit from a first aid place for the next few weeks.
Comments are welcome, too, but please post chit-chat elsewhere.

I already spotted a problem with Videos and VA-API acceleration: https://bugzilla.opensuse.org/show_bug.cgi?id=951150
Workaround is uninstalling gstreamer-plugins-vaapi if you have a fair CPU, or using Firefox for videos (no kidding).

Now I see that Nautilus 3.18 is not able to delete files from NTFS partitions mounted via fstab.
It offers to "delete immediately", since it is unable to trash files as in 3.16, but clicking "Delete" does nothing.
Moving files to another destination it simply copies them, without deleting the original.
Deleting from temporarily mounted pen drives seems OK.
I would like confirmation from others, before filing a bug report.