Despite the recent AWS S3 outage, I must say that Amazon Web Services rocks. I have spent the past month migrating a dozen WordPress sites in a multisite WordPress configuration from a regional hosting provider to AWS.
The performance gains are impressive. Granted, client sites were also moved from Apache to nginx. Nginx is small, extremely fast and ridiculously simple to set up. In the process we moved from a shared virtual private server (VPS) to a dedicated Ubuntu instance. Deploying a base Ubuntu image on AWS is quick and straight forward. All of this can fit easily into the AWS free tier, costing from $0.00 to $0.12 per month initially. We expect that once the free tier expires that our blazing fast WordPress implementation will cost less that $10.00 per month; a 21% cost savings over our former hosting provider.
The downsides to this approach include a little more complexity in deployment and management. For instance, we have given up access to cPanel requiring us to be a little more reliant upon the command line for things like MySQL, mail, DNS and file management, though in the future we may add in some Web-based management tools. Depending on how much (or how little) we really want to manage we may move DNS and mail to AWS managed services. This would, of course cut into our monthly savings but in the end, we get much faster performance and availability for our Web sites and a few less headaches managing our mail.
Next steps include implementing content distribution through CloudFlare and squeezing out even more performance gains and cost savings by deploying nginx as a reverse proxy.