As far as the docs, yeah it's up there with the FreeBSD guys and Gentoo as far as completeness goes.
How is Gentoo? I've never used it myself but I've been interested in trying it.
Gentoo is... how to put this diplomatically... If you have special needs as far as compiling or you want to have a build framework for creating your own distro Gentoo is great. If you want to tinker for the sake of tinkering Gentoo is great. If you just want a working system or you think compiling everything will give you a super mega speed boost, you might want to avoid it.
To give you an idea I can get my standard Arch setup up and running in under 15 minutes, if I wanted to do the same in Gentoo it'd take closer to 15 hours and I'd end up in almost exactly the same place for no real gain.
As for kernel setups, http://kernel-seeds.org/ can take some of the pain out of getting the hang of them