After more than a year and a half of development, elementary OS 0.3 ( codename Freya ) has been released on Sat April 11th, bringing three new default apps, a new notification system, a redesigned multitasking view, UEFI/SecureBoot support along with many other improvements and over 1,100 bug fixes. ( link )
elementary OS Luna users should back up their data and perform a clean install.
The same applies to the users of the beta version of Freya according to the developers of elementary.
If you as a Freya beta user don't want to do a clean install you could to the following to upgrade from beta to stable Freya :
Open a Terminal and first remove the beta PPA's :
sudo add-apt-repository --remove ppa:elementary-os/daily
sudo add-apt-repository --remove ppa:elementary-os/testing
Add the stable PPA :
sudo add-apt-repository ppa:elementary-os/stable
sudo apt-get update
Now remove elementary beta packages :
sudo apt-get remove elementary-os-prerelease
Update Linux kernel to 3.16 ( I skipped this step ) :
sudo apt-get install --install-recommends linux-generic-lts-utopic xserver-xorg-lts-utopic libgl1-mesa-glx-lts-utopic libegl1-mesa-drivers-lts-utopic
Upgrade the system :
sudo apt-get dist-upgrade