Thanks for sharing your setup regarding asset packaging for your rails app (very helpful).

I understand the relationship between CloudFront and S3 and should have been more clear with what I was asking: what is the quantitative difference you've seen in using CloudFront for asset delivery (js+css) versus just using S3? Your pages loading 100ms faster, but at a cost of X dollars more per gigabyte? Certain regions not being able to hit S3?

This sort of bleeds into the "when should I use a CDN?" question. There are lots of recommendations for people using Rackspace Cloud Servers, Slicehost, Linode etc. here on HN. With those hosting providers, I think most people would start off hosting on their local VPS and then at some point say: "I've got to get some of this on a CDN". What was the trigger for your app?