One minus that forced me to move away from Amazon EC2:
- spamhaus.org lists whole Amazon EC2 block on the Policy Block List (PBL)
This means that all mail servers using spamhaus.org will report "blocked using zen.dnsbl" in your /var/log/mail.info when sending email.
The server I run uses email to register and reset passwords for users; this does not work any more.
Read more about it at Spamhaus: http://www.spamhaus.org/pbl/query/PBL361340
Summary: Need to send email? Do not use Amazon EC2.