won't work for all kinds of apps. Coz, there'll always be menu heavy apps like GIMP, Inkscape, LibreOffice and other such suites. And there's apps from other desktops and frameworks too: KDE, Qt, Mono, etc and legacy stuff like GTK2.
So, converting all apps to use headerbars
doesn't seem practical in the near future. However, for those apps that are designed to use headerbars, they work well.😊 Hopefully, more desktops'll offer support for headerbars
in the future, like KDE's DWDs: https://plus.google.com/+HEXcube/posts/cJNB5tufN8d