Even worse than the $600 a month, there's no way to disable ssl on your site if you're serving off cloudfront, so if one of your users makes an https request and you're not shelling out the cash for custom certs they'll be greeted by a big red warning page in chrome (returned cert for *.cloudfront.com).
This is actually a great point against using custom domains (CNAMEs) with Cloudfront. At least if you can't afford the custom SSL certficate option.
Cloudflare somehow got this right. They serve non HTTPS enabled web sites with different IP addresses so that you can never reach them over HTTPS (could be better "This webpage is not available" vs. scary red "This is probably not the site you are looking for!" message in Chrome). Plus, they have a great free anycast DNS network that can be compared to Route 53. And best off all, you never pay for the bandwidth.
