I wonder if they're looking to achieve easy speedups. I can see lots of value enabling performance gains where normally people wouldn't bother because it's too much effort. I don't think this will take away work from those who hand-optimise their kernels and scheduling, this is to enable GPU acceleration for those, who otherwise wouldn't.

> It claims to be "sufficiently fast by default", yet "sufficiently fast" depends entirely on the requirements of a specific user project.

I think that's why the "by default" is there; the goal is to offer a safe/convenient API that performs well enough that by default you don't need to reach beyond said safe/convenient API. And if you happen to be in a situation where the default performance of the safe/convenient APIs is insufficient, more advanced APIs will be provided.

It's a mirror of Rust's general design goals, if anything.