I gave the Elementary Luna OS a try for November, which is based on Ubuntu 12.04. The Elemenatry OS distro uses the Pantheon desktop. It looks great, is extremely fast, and used 450 MB of memory. It does not come with many applications, but my usual favorites are available in the Ubuntu Sofware Center for download.
You can download the Elementary Luna OS here:
http://sourceforge.net/projects/elementaryos/files/
