Ubuntu 15.04 codename “vivid vervet” has been released and announced by canonical. it now available to download and install on your computer
This release include a Unity version 7.3 with bug fixes and errors, Compiz 0.9.12 with support for alternative desktop environments, and powered by kernel 3.19. also include a configuration option for Unity to have menus displayed at all times instead of only on mouseover, Enable the Dash, HUD, or logout dialogs over fullscreen windows and tweaks to animations for faster startup and shutdown experiences
Ubuntu 15.04 uses systemd instead of Ubuntu’s own Upstart system. it replaced Upstart as the standard boot and service manager on all Ubuntu flavors except Touch.
Default application that included in ubuntu 15.04 : LibreOffice Suite version 4.4, firefox 37, nautilus 3.14.2, GNOME packages 3.14, Ubuntu Software Center 3.10, Rhytmbox 3.1, and more..
More detail about this release you can read on Ubuntu 15.04 release notes