The behavior of the site switcher, inbox and achievements drop-downs in the new top bar seems inconvenient and unintuitive to me. I would like to propose a change to it.
Every drop-down menu opens when clicked, and closes when clicked again. If any drop-down menu is clicked while another menu is open, the previously open menu should be closed and the new one should be opened.
The drop-down menus in the new top bar are not hover menus. They should not be affected in any (non-cosmetic) way by hovering the mouse cursor over them.
Every drop-down menu opens when clicked, and closes when clicked again (as expected).
If the help drop-down on the right is clicked while one of the left-hand side drop-downs (site switcher, inbox or achievements) is open, or vice versa, the previously open menu is closed and the new one is opened (as expected).
When one of the left-hand side drop-downs is opened, the other two magically turn into hover menus: hovering the mouse cursor over them opens the new menu and closes the previously opened one. This feels inconsistent and unexpected to me.
As a side effect of the above, if one of the left-hand side menu icons is clicked while another menu is open, both menus close!
The last effect is, IMO, the most annoying one. It's most easily noticeable on touch screens, where touching the icon immediately triggers a click without any preceding hover period. However, it's possible to observe this effect on conventional desktops too, since, depending on network latency, some of the menus can have a brief delay before they fully open when hovered over for the first time.
Ps. If the current behavior is kept, it might help if the styling was changed to make it clearer that clicking one of the menu icons "activates" all of them. It would still be annoying on touch-screen devices, though.