The dashboard doesn't load, nor does content using the generic S3 url [1], but we're in us-west-2 and it works fine if you use the region specific URL [2]. In practice this means our site on S3/Cloudfront is unaffected.
Good catch. My bet is that because s3.amazonaws.com originally referred to the only region (us-east-1) the service that resolves the bucket region automatically is really hosted in us-east-1. I think AWS recommends using the region in the URL for that reason, however that is easier said than done I think. I would bet that a few of Amazon's services use the short version internally and are having issues because of it.
[1]: https://s3.amazonaws.com/restocks.io/robots.txt
[2]: https://s3-us-west-2.amazonaws.com/restocks.io/robots.txt