systemd is replacing Upstart
systemd is replacing upstart in Ubuntu 15. systemd is going to be there on the desktop, server and cloud version of Ubuntu except Ubuntu Touch.
It will be using Linux kernel 3.19.3 which has better graphics support.
GTK 3.14 support
Ubuntu 15.04 brings GTK 3.14 supports. Which means you can install various newly developed applications such as vocal in Ubuntu without using a staging PPA
More development tools
With Ubuntu 15.04, Ubuntu Development Center has been transformed into ubuntu make. For developers of mobile apps, web applications and games, it provides support for 14 new platforms including Android NDK, Android Studio, IDEA (ultimate and community editions), pycharm (professional, educational and community editions), webstorm, rubymine, phpstorm, eclipse, Stencyl game development platform.
‘Snappy’ Ubuntu Core
Ubuntu 15.04 brings the first stable version of ‘Snappy’ Ubuntu Core.
Local menus are back
Local menus are coming back as default in Ubuntu 15.04. It also means that global menu won’t be enabled by default in 15.04. You can enable the global menu in System Settings -> Appearance -> Behaviour tab -> ‘In the menu bar’ option.
Files (Nautilus) 3.14 brings couple of new features
15.04 also has the latest version 3.14 of Files (previously known as Nautilus) file manager. You can notice a minor change in the look in the left sidebar where mounted drivers are segregated in a cleaner way:
The new version of Files also has the option of Open in Terminal option in the right click menu.
Option to save WiFi password
Another minor change you might notice is that Ubuntu 15.04 provides you option to save the WiFi password either for the current user or for all the users. A very minor change but might be useful for some.
Needless to mention that Ubuntu 15.04 has updated versions of most of the applications such as LibreOffice, Totem etc.