The Sabayon Linux 14.05 release features a new "Steam Big Picture" install mode with the distribution already pre-installing Valve's software, support for deciding between binary and source based package management, new native NVIDIA and AMD GPU drivers, and it ships the Linux 3.10 and 3.12 kernels.
When it comes to the NVIDIA and AMD GPU driver support on Sabayon, the very latest NVIDIA and AMD blobs are shipped. When using AMD hardware though it defaults to using the open-source AMD driver but will automatically setup the Catalyst driver if booting the system using the nomodeset flag. For NVIDIA hardware, it's understandable they boot straight away to the NVIDIA blob given the Nouveau driver still lacks re-clocking support, etc.
More information on Sabayon 14.05 can be found via the official release announcement at Sabayon.org.