I just created a ticket for this issue:
http://dev.vaadin.com/ticket/16473
but posting here in case someone else is having the same issues I was having.
It took me the better part of a week to nail down that it was not a bug in my code but rather a regression in the way the SASS compiler generates its code. Of course, it didn’t help that I’m no CSS expert. For now 7.3.7 seems to be generating the right stylsheet.
Update- According to Jouni’s response on the above ticket. this is a change in 7.3.8 forward.
So, in order to use responsive valo-menu in your application you neet to call addStyleName(ValoTheme.UI_WITH_MENU) on your UI.
Good find, Iyad. I’ve just come across this problem in the past week and have narrowed it down to the compilation of the stylesheets however you’ve save me and probably many other developments days of wasted effort. 