For comparison the default GTK toolbar/menubar: 
If you are unsure wether you like this, just enable the plugin to have a look, disable it again and you will get back the default look.New gtk headerbar plugin
Yesterdays release (1.12.3) includes a new plugin that allows you to completely switch out the toolbar/menubar window decoration for a GNOME style GTK headerbar. How it looks with headerbar plugin enabled: For comparison the default GTK toolbar/menubar: If you are unsure wether you like this, just enable the plugin to have a look, disable it again and you will get back the default look.
For comparison the default GTK toolbar/menubar: If you are unsure wether you like this, just enable the plugin to have a look, disable it again and you will get back the default look.