To be clear, I wrote the announcement, but don't work on compiler optimizations. Those that do tend to have a better idea than me.

But beyond that, it's ultimately about what you promise. Say something sped up compilation times 2x for most people, but slowed them 10x in a corner case. If you promise the 2x, the people for who it slowed down will be (rightfully) pretty mad.

None of these changes are as drastic as that, but still.