After switching to CloudFront CDN my PageSpeed and YSlow rating dropped for two reasons:
- JavaScrip/CSS are not compressed anymore
- no cache expiration for images
The rendered markup contains links like http://cdn.frightanic.com/blog/wp-content/themes/itheme2/js/carousel.min.js?ver=3.5.1 although http://cdn.frightanic.com/blog/wp-content/themes/itheme2/js/carousel.min.js.gzip?ver=3.5.1 does also exist. The S3 settings related to Content-Encoding as per http://goo.gl/SyjTo were set correctly by W3TC while uploading to Amazon.
If I understand correctly W3TC is supposed to generate links to the .gzip files for user agents that support it?
Update: one needs to set the desired headers manually in S3.