That's not a change log but new features are listed here http://www.ubuntu.com/ubuntu/whats-new
> I also don't see an easy way to upgrade from 12.04 which is what I currently run.
http://www.ubuntu.com/download/desktop/upgrade
I never had any problems with it but some people prefer a clean install.
Fire up Terminal and run 'update-manager -d' and it should show up.