[int_19h]

I don't see how TPL discourages the use of mutable shared memory any more so than a simple thread pool. Note: I'm not saying that it's not a higher level of abstraction, only that it's abstraction in a different direction (the one that has nothing to do with sharing or mutability).

I'm not surprised that TPL author discourages mutable shared memory and locks - this is the conclusion to which anyone dealing with concurrency a lot arrives sooner rather than later. But that's orthogonal to TPL design.

Now, PLINQ does attack the whole mutable shared memory thing head-on. But it's a much higher level of abstraction on top of TPL.