I've administered a few gentoo machines a few years ago and can attest that it's a major PIA. Or let me elaborate a bit, system failures that happened on gentoo didn't seem to happen on other systems, system failures that also happened on other system took significantly more time to resolve and required much deeper knowledge of system internals than debian, centos or whatnot.
When I finally moved everything to debian and my time spent on system administration tasks went down dramatically.