I use models from Opus through Haiku and down into Qwen locally hosted models.

I don't know how anyone could believe that Haiku is useful for most engineering tasks. I often try to have it take on small tasks in the codebase with well defined boundaries to try to conserve my plan limits, but half the time I end up disappointed and feeling like I wasted more time than I should have.

The differences between the models is vast. I'm not even sure how you could conclude that Haiku is usable for most work, unless you have a very different type of workload than what I work on.