"MyMethod can’t return an object of with the type name MyMethodResult."You're fracking kidding me right? Wow. (and there are more along these lines)
After fighting with the above and other bugs I was rewriting a lot of the generated code from FlexBuilder and it was just pointless. And sure, generated code isn't the greatest to rely on anyway, but give me a break. In the end I used the WebORB presentation server to handle the communication to our .NET code, as well as for generation of the initial proxy classes for the client and I have to say it was an excellent experience compared to the crap built into FlexBuilder.