I'm using a multisite install and so have "My Sites" in my toolbar.
When I'm browsing the admin section with my keyboard, I can expand the "My Sites" menu with Enter. However, when I then select either "Network Admin" or any of my sites and hit Enter again the submenu closes and nothing happens.
Funnily enough: When I then hover over "My Sites" with my mouse, the "Network Admin" submenu does appear right away. Unfortunately, this does not seem to be the case when I try to tab back into the "My Sites" submenu.
Occurs in Chrome 36 and Firefox 31. Haven't tried IE yet.