Ubuntu 12.04.4 LTS makes available the Linux 3.11 kernel, packs in Mesa 9.2, and has other X.Org stack updates. There's also other minor new package updates like to Mozilla Firefox and Thunderbird.
Ubuntu 12.04.4 LTS also incorporates all of the latest security fixes and other stable fixes in a nice new ISO form.
The Ubuntu 12.04.4 LTS release announcement with all of the details on this latest Long-Term Support update can be found on the ubuntu-announce list. Meanwhile, Ubuntu 14.04 LTS is set to be delivered in April.