We just launched a site for one of our clients on ML 7.1 (will be upgrading to 8 soon enough).
http://www.naturalbundles.com/
This is also our first site running completely on Amazon's EC2 environment. We built some custom tools to take snapshots (backups) of the machine and can quite easily spin up another server with the appropriate configuration in case of catastrophe.
Not sure if anybody else out there is toying with EC2, but it's working quite well so far!