A Developer's Introduction to Workflow Foundation 4.0 in .NET 4.0 beta

"In version 4 of the Microsoft® .NET Framework, Windows Workflow Foundation introduces a significant amount of change from the previous versions of the technology that shipped as part of .NET 3.0 and 3.5. In fact, the team revisited the core of the programming model, runtime and tooling and has re-architected each one to increase performance and productivity as well as to address the important feedback garnered from customer engagements using the previous versions."