Interesting. Root level cnames go against the RFC spec, yet it seems this solution is technically on par. Looking at the linked site, users mark the root as an A record and then select a new option in Route53 called 'Alias'. Since many DNS providers enforce actual A records, sounds like route53 will often be required for this feature (not a show stopper for most, just checking).

FTA: "In the Amazon Route 53 Management Console, create two records for your domain. Create an A (alias) record in the domain's DNS hosted zone, mark it as an Alias, then choose the value that corresponds to your root domain name.

Create a CNAME record and set the value to the S3 website endpoint for the first bucket."