Just discovered that Transmit 3.7 has S3 support. You can manage it using the Advanced Preferences tab which you access by holding down the Option key while clicking on the Transmit application menu. From there you will see an extra preference tab where you can manage server connections and S3 settings. Now if they only added a tab for managing public keys for SCP/SFTP. For this you have to make sure your key is available @ ~/.ssh
