Hey Danny, thanks for the reply!
Performance should absolutely be a concern and while I think it’s reasonable to have this layer - it’s defintely not as quick as not using it! 
And this stuff isn’t my day-to-day so I’m sure there’s time that somebody could squeeze out of it. I also completely understand the desire to deliver a clear and concise API for async work as well as future/promise concepts that represent the C++ standard behaviours.
I’d of course love it if it were accepted but this is mostly to close the loop on the conversation we had last year about the UE::Async::Tasks API.
Don’t hesitate to reach out if you’ve got any questions,
Dom