For me the mark of a good extension is when you get great support to go with it.
Setting up streaming from Amazon S3/Cloudfront isn't the easiest task in the world,
Rudolph the developer went beyond his remit in helping me with issues on S3 that weren't strictly to do with his Extension at all but more to do with me doing things wrong on S3. The extension isn't perfect, there are a few minor bugs but nothing too problematic and I have faith they will be fixed given the quality of the rest of the support I received.
If you need to stream or download content from S3 via protected links on your Joomla site then this is the extension for you.