I also use Haiku daily and it's OK. One app is trading simulation algorithm in TypeScript (it implemented bayesian optimisation for me, optimised algorithm to use worker threads). Another one is CRUD app (NextJS, now switched to Vue).
Are you saying Haiku is better than Sonnet for some coding use? I've used Sonnet 4.5 for python and basic web development (pure JS, CCS & HTML) and had assumed Haiku wouldn't be very good for coding.