It is a bit similar in concept to Gentoo but adds in a configuration management (CM) part. The current iteration doesn't take full advantage of the CM capabilities but we're working on it.

As far as building packages as compared to installed the distribution binaries... I've run into issues where the binary package wasn't compatible with libraries and apps that I had to install outside of apt-get or yum. For instance setting up reasonably modern Rails configuration with all the gems I needed on a Ubuntu 10.04 server.

I've also done builds and software configuration management for a living so the whole process is more like second nature at this point.

What you do want to avoid is a constant cycle of having to upgrade and build existing and working environments just to have the latest versions. At that point you do need to step back and evaluate if it's really necessary (security, fix, etc.).