[ahepp]

My experience:

It's very easy to overengineer. Both the SOAP WS-* extensions, and the underlying XML.

The tooling and ecosystem suck. I found it a lot more difficult to use clients like soapUI as opposed to just banging on a REST API with curl. The libraries are mostly java, with at least one c/c++ implementation. I had a lot of trouble getting different libraries to work together. And that's literally the entire point of SOAP. It's supposed to be the enterprise grade interoperability (of course, a huge oxymoron) compared to REST.