I'm part of a 7 figure project right now. We're a .Net shop, they have a Java infrastructure (and are as "enterprise" and process-laden as you can imagine and then some). We need to integrate -> See, we're right there.

SOAP it is for us and I do have to say that I'm rather relaxed. For us it's just one way (Java services, Java generated WSDL, we just consume/use the stuff), but it works rather well.

Unless you don't know about 3.5/WCF/Service References and try to do it the old-fashioned "Web Reference" ASP.Net way: That's a royal pain and just plain doesn't work at all for some (valid) SOAP things (some sequences of alternating complex types a la [Key, Value, Key, Value,...] for example cannot be mapped). Guess how I found out..