Certain programs, like the TAHI organizations v6eval package will fail to compile. This means the recent 9.0-RELEASE of FreeBSD will no longer work out of the box. This really only required a minor change to get it working. I've published a patch here.
EDIT: ed@ kindly worked up a functional patch that works with utmpx's binary format, this might explain why sometimes your child processes are left hanging after a run: