This is really something, especially for small apps. S3 is now the easiest KV store I can imagine.
Even the big ones. A lot of applications (e.g backup vendors) had to resort to use EBS volumes because of lack of read-after-update consistency.
The barrier to entry for lot of developers has been reduced.
My prediction: A lot of storage infra (FS, DB) with native support for S3 will get commoditised now.