They tried to be bleeding edge and could not keep up, up to a point where they did not even ship current packages in the stable tree (e.g. when all others shipped mySQL 5.0, and Gentoo didn't even have a mySQL 5.0 ebuild in the tree). Later on they focused on having a bleeding-edge stable tree, but that also didn't work - Ubuntu and Fedora do a better job.
Not only is Ubuntu Testing more bleeding-edge than Gentoo ever was, it also ships a much larger number of packages which are actually built for every supported platform. The Portage tree contains many broken and outdated ebuilds, and most of them are not marked for architectures other than x86 and amd64.