Per this SO question. StephenCleary states not to use Async Compatablity Pack.
When researching this more fully I have come across MSDN posts on how to use it and why, I have come across SO posts on how to use it and best practices, and the NuGet Gallery states that it is designed for .net 4.0
Why would this not be recommended by someone who wrought the book Concurrancy and C#?