As you probably know, in the current stable Ubuntu releases (12.04, 14.04 and 14.10), the Unity (global) menus are displayed on mouseover for both the default menu that's displayed on the top Unity panel and LIM (locally integrated menu), which is displayed in the application titlebar.

With Ubuntu 15.04, there's a new option (not enabled by default) which allows setting the Unity menus to always be visible:

Unity developer +Marco Trevisan is working on some tweaks for Ubuntu 15.04 Vivid Vervet and among them, there's a fix for a three year old bug related to Unity's menus. 

Marco's work involves adding an option to always show the Unity menus (in Unity, the menus are currently displayed on mouseover). Furthermore, this option will work with both the regular Appmenu / global menu, displayed on the top Unity panel, as well as LIM (locally integrated menus), displayed in the application titlebar:

JAyatana version 2 was released recently, getting support for Ubuntu 13.10 along with a PPA for easy installation. Update: the PPA now supports Ubuntu 14.04 and 14.10.

GNOME has introduced the AppMenu for some of its core applications a while back (for some applications like Epiphany, with GNOME 3.4 and for others like Nautilus, etc. with GNOME 3.6), meaning that part of the menu or the whole menu is displayed as a drop-down on the top GNOME Shell bar:

By default, the popular Eclipse IDE does not support the Ubuntu AppMenu or  HUD. The reason for this is that Eclipse has been blacklisted so it wouldn't use the AppMenu around the time of Ubuntu 10.10 Maverick Meerkat because it didn't work back then.

Now Eclipse does work with the AppMenu, however, there are some minor glitches like some menu shortcuts not being displayed (although they do work). If this isn't a problem for you, here's a quick way to whitelist Eclipse so it can make use of Ubuntu's Appmenu and HUD.