...and Alpa Agarwal, a colleague of mine answered:
The Concurrency and Coordination Runtime (CCR) and the Task Parallel Library (TPL) are complementary technologies. TPL, which provides support for imperative data and task parallelism, is well suited for synchronous parallelism and patterns such as parallel loops. The Concurrency and Coordination Runtime is well suited for orchestrating many asynchronous components and handling asynchronous I/O in a clever manner. Though TPL and CCR may seem slightly redundant on the surface, we encourage you to try our CTP of Parallel Extensions to the .NET Framework and to provide us with feedback.