Probably related to the post - We have solution for integrating SAP ECC (R/3) back-end with Magento e-commerce. We have made it comprehensive and followed the best practices recommended by SAP. As we detailed out the solution it led to 40+ integration aspects. Probably this is why its getting so widely accepted by customers.
View the demo, read success stories and get the pricing details by clicking on the link. http://www.veonconsulting.com/sap-ecc-magento/
So far as the technical aspects are concerned we have used ALE/RFC and web-services. It also uses a hybrid agent for integration without sending any information / transaction details to the cloud.
Thanks for your attention!