The good stuff starts around 7:30!
S3SwfUpload allows user to upload a file to S3 directly, so you can save the cost of uploading process in your app server.
The flex application in this fork was completely re-written so that there are no flash or flex UI components. The one exception to that is the browse button, which, for security purposes MUST be flash. But even then, you get to pass the URLs for images to use for that button!
Please note: As of Nov 2010, the rake tasks used in this example video no longer work. They were removed to eliminate the dependency on aws/s3