That's just one of many changes inside Vivid Vervet, however. The latest release of Ubuntu also features re-revamped menus, some important desktop improvements, a new version of LibreOffice, and features for developers, servers, and phones. Also worth noting is a change that isn't included: Ubuntu 15.04 still contains the Unity 7 desktop environment. The converged version of Unity 8 — which will connect Ubuntu's mobile and desktop interfaces, switching between them dynamically when needed — scheduled for a future release.
Locally integrated menus
The first difference you'll notice about Ubuntu's desktop are its "locally integrated menus." (Actually, the first thing you'll notice is the new, purple-ish default wallpaper. You'll notice the new menu system second.)
Despite the awkward name, this feature is easy to understand. Long ago, Ubuntu moved the in-application menus out of each application window and to the top of the screen, on the desktop-wide menu bar. Now, for usability, these menus have been moved back inside each application's individual window. They appear in the application's title bar, and you'll have to hover your mouse over the left side of a window's title bar to see them.
This does seem a bit silly, like change for the sake of change; the menus were moved up and then back down again, except they ended up in the window's title bar this time. But hey, it's a bit of an improvement. This arrangement does make those menus take up less screen space.
Making the desktop aware of these menus also powers Unity's HUD. Tap the Alt key and start typing to search the current application's menus for an option and quickly activate it, all from your keyboard.
If you prefer the old system, you can open the System Settings window, click Appearance, select the Behavior tab, and choose the "In the menu bar" option under "Show the menus for a window." There's also an option to always show the new menus rather than having them auto-hide inside application title bars, but it's buried deep. You'll have to install the Dconf Editor application, launch it, navigate to com > canonical > unity, and enable the "always show menus" option.
Systemd, LibreOffice, and Ubuntu phones
Ubuntu 15.04 uses systemd instead of Ubuntu's own Upstart system. This is an under-the-hood issue more than anything else, and systemd has been tested extensively. You shouldn't even notice the change as a typical user — even though the inclusion of systemd in Debian was divisive enough to spark a new "Devuan" fork stripped of the project's code. But consult Ubuntu's "systemd for Upstart users" guide if you're a system administrator or someone who's created your own Upstart jobs.
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