We run the latest mainline kernel on all our 200-300ish CentOS hosts after it's passed standard testing and is available in Elrepo: http://elrepo.org/tiki/kernel-ml

Back when we ran Debian everywhere I wrote a CI project that would build the latest mainline kernel, applying GRSec and adding some SELinux policies in as best I could (backported from CentOS/Fedora funnily enough) and build them into a Debian package for deployment across our hosts, see: https://github.com/sammcj/kernel-ci