I am running a test with W3 Total cache.
First of all, I am very impressed with what it does, kudo's for the brains that put it together.
Now W3TC has the possibility to use S3 as a CDN, very cool.
I prefer to use the Reduced Redundancy Storage option for this, since it is cheaper and all data is backupped anyhow. Transmit, Cyberduck and bucketexplorer have the ability to set RRS as default, by sending custom headers.
Is there (or will there be) an option in W3TC to do this? What I did now was use W3TC to upload the data and then change the storage type through the AWS management console,which takes a lot of time and does not always go well.