(I did a quick test, and I'm seeing between 15-20% for https://github.com/servo/stylo which is a macro-heavy crate. I guess it only matter for crates you're actually editing though, macro will already be cached as part of "entire crate is unchanged")

> Another thing that can easily improve performance is changing the global allocator, but I've seen teams that measured 10% perf improvements in their own metrics decide against going with anything other than the "default".

Yeah, although I think there's more of a trade-off there. Alternative allocators can add significant amounts of compile time. Whereas, modulo maturity, I think a faster linker is more of a pure win. I would imagine we will make wild the default linker at some point if development continues on the trajectory it seems to be on.