I agree with you, the context changes nothing (and I upvoted you for this reason). However programming languages and infrastructure pieces like this are a bit special, in that optimizations here are almost never premature.
* Some of the many applications relying on these pieces, could almost certainly use the speedup and for those it wouldn't be premature
* The return of investment is massive due to the scale
* There are tremendous productivity gains by increasing the performance baseline because that reduces the time people have to spend optimizing applications
This is very different from applications where you can probably define performance objectives and define much more clearly what is and isn't premature.
I don't know about that. Even with your programming language/infrastructure you still want to identify the slow bits and optimize those. At the end of the day, you only have a certain amount of bandwith for optimization, and you want to use that where you'll get the biggest bang for you buck.
