I see on Launchpad that there is release 0.4 Loki. Is this available for download?
If so, is it the same installation (i.e. with an ISO) or is it a more technical process?
Yes, elementary OS Loki has been released. For the latest version of elementary OS, you can always visit elementary.io.
NOTE: These directions are unofficial, outdated, and not supported by elementary
First, download Ubuntu 16.04 from http://cdimage.ubuntu.com/daily-live/current/ and install it. Then in Ubuntu 16.04 terminal run the following commands:
sudo add-apt-repository ppa:elementary-os/daily sudo add-apt-repository ppa:elementary-os/os-patches sudo apt-get update && sudo apt-get dist-upgrade sudo apt-get install elementary-theme elementary-icon-theme elementary-default-settings elementary-desktop
Then you should be able to select the new desktop environment in the Unity greeter.
Maybe someone can make an ISO from this.