I have no doubt that Amazon usage of their own advantages is better than goamz.
SDK usage is all about the getting started and the documentation. For me, building an open source project around the Amazon SDK was just too much.
Obviously, documentation will solve a lot of this. I did not visit the project in months, maybe they improved on this.
This is a huge problem when you're trying to upload several million tiny files as quickly as possible.
When I switched to Amazon's official S3 library, this problem went away.