That being said there are also a lot of applications where the menu is used rarely enough that exposing the first level of menus isn't worth the screen space. In this case I think a hamburger menu is fine. For example in Firefox I rarely use the menu. Most things I do are keyboard shortcuts, or the couple of things I have moved to the toolbar. And I often wish I could see more at the same time. I think the main issue with Firefox is that the menu is basically impossible for a new user to find. I believe the only ways to bring it up (on Linux at least) is tapping Alt or Alt-<m> where m is a mnemonic that you would have needed to see the menu before to know. I guess this is their way of slowing killing it off in favour of their hamburger menu, but I find the hamburger menu has way less options and is way harder to browse. It feels more like a place for frequent options rather than a full menu. As much hate as there is for 3-level menus the actual browsing UX was quite good.