I have seen the questions about the differences between BizTalk and WF and "when to use what" have been raised multiple time. Based on my experiences with both technologies and my readings (some listed below), I summarized the usage scenario as follows...

In the past four years, together with other fellows at BAM team, we helped build the BAM feature from ground up. The groundbreaking BAM v1 was first shipped with BizTalk 2004 and the much improved, highly anticipated v2 is to be shipped with BizTalk 2006...