What's holding back the Workflow Foundation from being mainstream at this moment?

It is at the core a development tool, oriented for developers -- not business analysis, domain experts, product managers or end customers. As soon as you deviate from the garden path, you need to be a hard core developer. At some point I assume this will get better.

What are some of the biggest and best changes you have seen over the evolution of .NET?

The addition of generics, ClickOnce and the transaction infrastructure of .NET 2.0

What's in store for the future of SOA's?