[eip]

Doing a 'hardComputation' async provides no advantage. The cpu is limited to how much computation it can do and if you have enough of those 'hardComputations' running simultaneously whether sync or async you will hit the limit of the cpu.

Async is only beneficial in terms of IO.

[eropple]

Preemptive multitasking makes this much more valuable than you portray it. Play also makes it really easy and you don't have to seriously think about it.