Translations:FAQ/25/en
From Gentoo Wiki
In fact, there is no difference between the various releases after they have been installed. Gentoo 1.4 and later are glibc-2.3.x (or higher) based. As such, running emerge --sync && emerge -uDN @world will bring the entire system up to speed with the "latest Gentoo". The differences between individual releases lie in the installation medium and pre-compiled packages. See the Gentoo Upgrading Guide for more information about profiles and their role in upgrading.