It’s since March 2007 that WCF and WF started their mind meld (remember Orcas?) and I am tempted to say that in the .NET Framework 4 the process is pretty much complete. Want proof? You can use WIF for handling access to a Workflow Service just like you would do with a classic pure WCF service. Want even more proof? Zulfiqar put together a great post which walks you just through that. Check it out!