I saw this MSDN mag article by Aaron Skonnard a while ago, and am now revisiting it to understand the differences between WCF, ASMX 2.0 and WSE 3.0, especially as they relate to SOAP protocols and compatibility with older non WCF-aware clients (think VB6, ugh)

There are some good Q&As in here, along with a table (figure 4) that describes the diffs.

Service Station: All About ASMX 2.0, WSE 3.0, and WCF -- MSDN Magazine, January 2006