Raspbian, the de facto operating system on the Raspberry Pi, got a big update today. The update's based on the most recent version of Debian, called "Jessie," and brings along a bunch of minor interface tweaks and performance improvements.
The most obvious change you'll notice out of the box is that Raspbian now boots directly to the desktop GUI and not the command line (of course, you can always change this). That desktop has a bunch of tweaks to the menus and looks a bit more modern than before. Alongside the new look comes performance improvements, namely with desktop software like LibreOffice and Claws Mail, which run much better than before, especially if you're using a Raspberry Pi 2.
You'll also find some new settings options, including a GUI version of the raspi-config menu, which is a heck of a lot easier to use for new users. Check out the full blog post on the Raspberry Pi Foundation's page for all the new stuff.
Jessie Is Here [Raspberry Pi]