OS for new computer?

I'm leaning heavily towards Gentoo since it's what I know, but has anyone got any other suggestions? Frugalware looks interesting, I always approve of any project with a Keep It Simple philosophy, but I'm used to having a powerful package manager, and I don't know anything about pacman. Is pacman particularly powerful? Does it resolve dependencies etc?

It's an Athlon64 btw and I do intend to use a 64 bit OS.

>>4
It's more like a knee-jerk reaction a lot of geeks have.