Comment 3 for bug 571271

I've verified this with:
$ ec2-run-instances ami-2d4aa444
$ ssh host

% echo deb http://archive.ubuntu.com/ubuntu/ lucid-proposed restricted main multiverse universe |
   sudo tee /etc/apt/sources.list.d/lucid-proposed.list

% sudo apt-get update
% sudo apt-get install cloud-init
% sudo rm -f /var/lib/cloud/sem/*
% sudo reboot

# now instance comes up with different ssh fingerprint (indicating that the cloud-init re-ran)

$ ec2-get-console-output i-XXXXXXXX | grep "cloud-init run"
cloud-init running: Fri, 14 May 2010 12:49:55 +0000. up 5.41 seconds^M

That shows new code ran.. I've also verified that the wait is longer if, by chance, the metadata service is not there.