The point that make gentoo a bit better is to give me choice to install what I want but ubuntu doesn't. Say, I want gnome but not evolution / mozilla and whole lots other; which ubuntu, its already there and I fear of apt-get remove will get me in trouble, meanwhile, with gentoo just emerge gnome-light and eventually install what I want :))
If you can't remove evolution without breaking GNOME, then it's a packaging bug in Ubuntu and I'm sure they would love to hear from you. Your original question was regarding AMD64; there is no Gentoo specific advantage on a 64 bit arch; being able to start from a base applies equally to any 32 bit arch as well! So if you want Gentoo go to Gentoo, but don't think that you have to because you are on a 64 bit platform.
Basically, I don't want to wait :) b'coz to me, there is no deadline in OSS.
While that is in the most part true, with 6 month release cycles fast becoming standard, you might find that all the good stuff gets committed just before releases of things like GNOME, Fedora & Ubuntu. Craig