So while Dan Rabbit’s elementaryOS is still considered a “work in progress”, you can, however, with the help of Ubuntu 12.04 set up the needed PPA’s and get yourself this new Desktop Environment and play with it. It should be noted that “luna” is considered “unstable”, but I will be honest with you, I have not really had any issues with it what so ever, or at least nothing that a sudo apt-get update && sudo apt-get upgrade could not fix.
So the first thing that you need to do is to go download an ISO of 12.04 from Ubuntu. It is possible to do an apt-get dist-upgrade, however, I had better results when i did a fresh install, so YMMV. Once you get the disk image for your processor type (if unsure, get the x86/i386 version), and you can either burn it to a disk (easy way to do so) or use any number of various tools to “burn” the ISO to a flash drive, IF your computer can boot from a flash drive. Booting from a disc will take a bit longer and the install routine will be a bit longer also from disc, but it is the best and standard way to do this.
Hope you like it!