Check out this interesting Whitepaper describing an adapterless IDoc communciation between SAP NetWeaver Application Server and BizTalk Server 2004 SP1 -or- 2006, as long as you are running SAP NetWeaver AS 6.20 -or- 6.30 -or- 6.40 as an alternative in using the existing BizTalk Adapter 2.0 for mySAP Business Suite SPA (aka BTS SAP adapter) for SAP versions SAP 4.6D and below. This Adapter which is available for BizTalk Server 2004 with additional pricing, is free with BizTalk Server 2006 (as all the other adapters from Microsoft are free respectively included in the BizTalk Server 2006 price as well). That adapter builds upon the SAP .NET connector 1.0 and leverages RFCs to communicate with SAP. This integration is SAP certified via the SAP integration scenario CA-ALE 4.0.
Download Whitepaper: "IDoc based adapterless communication between SAP NetWeaver Application Server and Microsoft BizTalk Server, by Jürgen Daiberl and Tilo Böttcher, Global SAP-Alliance, Microsoft" at http://www.microsoft-sap.com/pdf/CollaborationBrief.pdf
Download Whitepaper using SAP XI and Microsoft BizTalk Server with reliable messaging thru SOAP: https://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/docs/library/uuid/7521a237-0701-0010-499b-b3285b789c0d
more information on BizTalk Server in an SAP environement can be found at: the Microsoft SAP Alliance website under BizTalk http://www.microsoft-sap.com/technology.aspx and also check out our SAP teams blog at http://blogs.msdn.com/saptech/