Here is some good news for those using AWS S3. Amazon has formally released a Service Level Agreement for the S3 service. Very nice!
From the AWS site...
AWS will use commercially reasonable efforts to make Amazon S3 available with a Monthly Uptime Percentage (defined below) of at least 99.9% during any monthly billing cycle (the "Service Commitment"). In the event Amazon S3 does not meet the Service Commitment, you will be eligible to receive a Service Credit as described below...
For the full details visit the SLA page. We can only hope soon they'll bring EC2 out of beta, give us choices for more powerful AMI's, and the follow up w/ an EC2 SLA. Should be interesting!