I ran ArchLinux for years, and before that I ran FreeBSD for several years, but I've been running Fedora and Gentoo for the three few years; so this was several years ago, which is to say Your Millage May Vary.
FreeBSD has a ports system, which inspired Gentoo's portage system if you're familiar with that. The source builds tend to be pretty up to date, not as much as Arch, but maybe closer to Fedora or openSUSE. They also provide binary packages which may be useful for some large packages (like LibreOffice and Firefox) or on old machines. I would say I like FreeBSD's ports over Arch's packages + AUR. There are better tools for working with Ports than the AUR, and the packages tend to be tested better. I never worried about a FreeBSD upgrade making my system unbootable, as I had regularly happen with Arch.
Personally, I would not run ArchBSD, or Debian GNU/kFreeBSD or even Gentoo/kFreeBSD (I'm running gentoo these days and loving it). Because the best thing about the BSD's is the stable core OS. FreeBSD isn't a Kernel like Linux, it's a Kernel + core userland. And those things are stable, with periodic bugfixes and security fixes only. Everything else is a Port or Package, and that's really nice.
FINALLY! Somebody with a comparison. Thank you so much for the answer.