This is the third build of Ubuntu 14.04 Long Term Service, this is the first build in this year, this build also has newer Linux Kernel 3.16 that was released in Ubuntu 14.10, and some better hardware support and improved Xorg display driver, the below are some improvements.
Kepler GPU support
Many fixes to Btrfs
hardware enablement stack will be available by default and run out of the box.
You can read the release note for more information here