The various SOAP and WS-* related specifications have the reputation of being tricky and difficult to understand. The latest project I am involved in requires a relatively deep understanding of WS-*. One way to gain understanding of a specification is by closely studying an implementation of it. Spurred by my previous pleasant experience with it, XFire happens to be that implementation of choice.
From what I can tell, the code is a pleasure to read and it feels like it is the result of fairly good design.