My product is AuditBadger.com - it's an AI-assisted compliance management platform (ISO27001 & SOC2) that guides you through the whole process (with everything a small business might want from such software). Having a few dozen customers allows me to still care about them personally and do onboarding for each and every one of them. During those onboardings, catch-ups, or weekly calls, I see where they struggle. This is how I determine what to work on next. There's no clear measurement of success beyond user satisfaction, though they every now and then praise me a little for UI/UX improvements. With Claude Design, I've got my design system set up (also by Claude scanning the repo); I upload a screenshot of the area I'm not happy with, prompt with some additional remarks, and after a couple of iterations, I get a proposal, which is always better than what I come up with in the first place.