in fact, i have in mind that Entropy not contain much packages of the gentoo overlays, except of the Sabayon's overlay and sabayon SVN... Therefore, Portage in Sabayon, still works with layman and gentoo overlays.
for an example ,i have one installation of sabayon, in wich E17 was installed from the enlightenment overlay.
also, it have another possibility, i use gentoo also, and somey years ago, i made this test:
if you use an old sabayon, 3.4F (it not have Entropy) only Portage.... you install it.... installed, you download the kernel of gentoo, compile it, install, change the kernel from sabayon to gentoo with eselect, then changing the sabayon artwork by gentoo artwork, change the KDE of the sabayon, remove the overlay sabayon, substituting by overlays of gentoo, changind KDE by XFCE, manage flags, recompileetc... as in gentoo etc... etc... You may "transform" Sabayon in Gentoo...!
Because, even now, an exception for Entropy (wich i see in the net that is installable in gentoo!) and for Paludis, that is not entropy compatible, sabayon is an gentoo, but an Gentoo with many many packages, because of this the emerge world may leeds to problems in Sabayon.
Also, i tested more than 40 distros, including Debian, Arch ans Slackware,
Now, i greatly prefer 3: Sabayon, Gentoo and Mandriva Free. I begin some tests with the Daniel's Robbins Funtoo, an modification of the gentoo, basically is a GIT oriented Gentoo.
ALBERTO FEDERMAN NETO
Favorite Distros: Sabayon, Gentoo, Mageia and OpenSUSE