Ask HN: What are your experiences of App Store optimisation?

Recently I’ve launched an app on the App Store which has had reasonable success and is getting great feedback from customers (5 star ratings etc).

I’ve had a number of agencies contact me to say they could increase downloads via App Store optimisation. What are everyone’s experience of attempting App store optimisation for SaaS products?

Specifically on the iOS App Store and in recent times (last year or so)? Has anyone actually seen a good uplift in new users and downloads?

With limited funds and time, I’m reluctant to expend $ on an activity which may turn out to follow a lot of the old-school web SEO scams and waste resources. Is ASO a good way to grow an app-based startup?