We have htmx & hyperscript running in production powering a fintech saas. It is fantastic in the way that all really good technology is: it just does what it's supposed to do so simply and efficiently that you kinda forget it's there, so you end up spending time where it counts (UX and business logic), instead of fighting finicky frameworks. No-one in the real world cares about the supposedly great framework powering a web app - they just care that the app is fast, easy to use and saves them time and money.