I remember so much pain trying to get a .NET WCF and Java SOAP service to work together when they should have been compatible. This is an amusing read: http://harmful.cat-v.org/software/xml/soap/simple :)
The UK National Rail API is a WCF SOAP endpoint so I wrote this open source proxy with Web API to make it easier for non-.NET developers more familiar with restful JSON: https://github.com/jpsingleton/Huxley