[The concept of a thread pool is not new, which is why Apple refers to GCD as being an instance of one. What is unique is the implementation, and that Apple has made it accessible to its developers.

As Apple explains, "GCD combines an easy-to-use programming model with highly-efficient system services to radically simplify the code needed to make best use of multiple processors. The technologies in GCD improve the performance, efficiency, and responsiveness of Snow Leopard out of the box, and will deliver even greater benefits as more developers adopt them.

"The central insight of GCD is shifting the responsibility for managing threads and their execution from applications to the operating system. As a result, programmers can write less code to deal with concurrent operations in their applications, and the system can perform more efficiently on single-processor machines, large multiprocessor servers, and everything in between. Without a pervasive approach such as GCD, even the best-written application cannot deliver the best possible performance, because it doesn’t have full insight into everything else happening in the system."

Introducing Blocks and Grand Central Dispatch

Also look at John Siracusa's overview at Ars Technica:

"Those with some multithreaded programming experience may be unimpressed with the GCD. So Apple made a thread pool. Big deal. They've been around forever. But the angels are in the details. Yes, the implementation of queues and threads has an elegant simplicity, and baking it into the lowest levels of the OS really helps to lower the perceived barrier to entry, but it's the API built around blocks that makes Grand Central Dispatch so attractive to developers. Just as Time Machine was "the first backup system people will actually use," Grand Central Dispatch is poised to finally spread the heretofore dark art of asynchronous application design to all Mac OS X developers. I can't wait."

- Dan]

I love the concept of GCD. It allows different processes to act independently and interact with each other and to make a decentralized approach to what the computer is doing. This is a fundamentally different approach than the “central truth” paradigm that most of the computer industry is using. For this reason it is absolutely impossible that Microsoft would adapt GCD, there is no way it would fit into their way of thinking.

I am amazed about Apples policy to what they do and do not open for third parties. They are absolutely secretive about the regular business chit-chat that everybody wants to know. But when it comes to the big clues about how things really work it is just openly available. And nobody seems to care…