OK, I know, my suggestion can be controverse, but it's necesssary.
In my opinion, Sabayon should be use open source graphics drivers as default. Closed graphics drivers doesn't provide a good compatibility with many graphics card. In case of nVidia, only GeForce 8 or more recent are supported. Ok, in the most cases is not a problem. But with AMD is a serious problem. Only Radeon HD 5000, 6000 and 7000 are supported, Also, the legacy drivers don't work with X.org 1.13. Another question: will Sabayon wait for an AMD's legacy driver for X.org 1.13?
This generates compatibilities problems, specially in the Sabayon's (post)instalation process. Result: no graphical environment loaded on startup. It doesn't combine with the "works OOTB's" philosophy. Nouveau and ATI drivers lack various features and have low performance, but they work on any situation.
For who wants the proprietary drivers, it's enough install mannualy using Entropy.