The attached patch includes the Hadoop EC2 scripts in contrib/ec2/bin. I think they are ready for inclusion in the main distribution now.
I have extended the scripts since the version in the tar.gz file by making them more robust: they no longer have to be unpacked and invoked from the user's home directory. More significantly, I have used a parameterized launch to set cluster size and master hostname. Previously, you had to build an image for a particular cluster size and hostname - now you can build one image and choose the cluster size and host name at launch time. (This is a step towards shared Hadoop images.)
As for the other improvements, I will create new Jira issues for them, since the basic scripts are in a working state (although I would love feedback if anyone tries them out).
James - thank you for the suggestion about Zeroconf. I've not had any experience with it, so any help would be appreciated.