Hi, I'm trying out gnome-flashback on Ubuntu Xenial 16.04, and I'll like to provide some feedback about whatever issues I discover.
1) Two nm-applets appear in the systray.
2) All gnome menus, for example the Applications menu or the Gedit menus, have a large (about 20 pixels) gray border around them. Thunderbird or pidgin don't have that border. I'm using metacity, not compiz.
3) Some dialogs (e.g. the "save before exit?" dialog of gedit) have their buttons (Close without saving / Cancel / Save) too wide, so that they fill the whole dialog width.
4) I would like to propose that the window buttons are restored to their pre-Unity settings, menu/minimize/maximize/close.