Disclaimer: participation in D 2.0 is possible after 10 days (tick "not using D regularly"). I believe this is an opportunity to learn something about D.
Regarding 1 and 2: Easy to read and understand ( writeln("Sum = ", myFuture.spinWait());probably should be in the example writeln("Sum = ", myTask.spinWait());).
3: a , . D, , - .
4:, , , , , , . ( , ). NUMA "" , "" . , API . : , , parallel_for ? D , ?
: , . ( ) . , :
( parallelism) ( parallelism). ++ (TBB, OpenMP, MS PPL TPL). , : (, GPU) (, ).
, TaskPool. , , . Intel TBB FAQ , :
[...] , . , . , TBB . , ; [...] k TBB k . , k, , - .