FYI in case anyone is trying to get phungus' upstart script working on Ubuntu 12.04. The runlevel config needed to change a bit. See below.
# bitcoind upstart script for Ubuntu
description "Bitcoin daemon"
start on runlevel [2345]
stop on runlevel [!2345]
respawn
exec su -c "/home/bitcoinuser/bin/bitcoind" - bitcoinuser