[hburd]

I agree with almost every one of your points. I think I oversimplified my original point for the sake of clarity.

If you are throwing out maintainable code for the sake of performance, it had better be because you know that it's your bottleneck, and that the performance increase is worthwhile in the first place. "Performance for performance sake" shouldn't exist anywhere outside of hobby projects.

I would argue that responsive user interfaces are really important to user experience. Not many people are complaining because everyone is used to unresponsive apps, but that doesn't mean users wouldn't appreciate a more responsive app.

I would also add that there isn't always a tradeoff between performance and maintainability. If you can adopt some performant coding patterns that don't sacrifice maintainability, then absolutely do that. I think Casey's example of "switch-based polymorphism" is one such pattern(and I think the fact that Rust took a similar route to polymorphism is a vote in favour of this pattern).