>Is there any software that you write whose users would not be made happier if the software performed better? Any at all?

I'd say security is a bigger issue than performance most of the time.

And most gains are going to happen within the code itself by, e.g., not writing n^2 when there's a log(n) solution or something similar.

Plus we're talking about javascript, and that's likely to be software with network concerns, so your optimizations might be a rounding error compared to performance degradation from slow network connections.

>You don't need to know any hidden instructions or secrets to take advantage of the platform.

You don't know what they do though. Some of those ops could be more advantageous to performance to use in some cases. You can't fully know the platform if there are secret ops.

You can still make optimizations with partial knowledge, but don't pretend to know the platform when the platform manufacturer doesn't tell you everything about it.

>The fixes also required no code changes outside of the firmware and the operating system, and knowing the platform is still the best way to write performant software, no matter what is going on to avoid hardware vulnerabilities.

Good algorithm knowledge and practice is the most cost-effective way of writing performant code and is more than likely going to be the lion's share of issues.