The AppMenu button in certain apps does not behave as expected. For example, click-and-holding the AppMenu button in Midori, Postler, Dexter, or Purple accomplishes nothing; the menu shows up after "unclicking" the button.
The expected behavior is exhibited by click-and-holding the AppMenu button in Nautilus-elementary, which then shows a dropdown menu and allows the user to mouse to an item, then unclick, choosing the item. This is also how the menu in Chromium works, as well as various other buttons in AbiWord and Gnumeric. The menubars (in apps that have them) work this way, as do menu items (main menus, indicators) on GNOME Panel and WingPanel. This is also similar to right-clicking where one can right-click-and-hold, mouse to the item, and unclick on the item they choose.
Well this is basically just because each app currently (for the most part) uses their own implementation of AppMenu. NautilusElementary at least does. Hence why I created elementary-widgets, to standardize.
I will fix this in elementary-widgets upstream, but it will be up to individual devs to implement the changes.