Thank you for the feedback! Most of the credit for the speed goes to the amazing Rust modules 'ignore' and 'regex', which are also used by ripgrep (https://github.com/BurntSushi/ripgrep).
That has certainly been my experience in the past when experimenting with this sort of thing, that more threads makes a lot of difference.
I did. You are right, multi-threading does not give a linear speed up, but it makes fd about a factor of three faster on my machine (8 virtual cores). With `--threads 1`, fd is on-par with 'find -iname', but still faster than 'find -iregex'.