I, for example, would love a service that would let me create a pdf invoice with a simple PUT or POST. I don't need a payments solution, or bookkeeping software, or a recurring billing service. Stripe gives us 95% of what we need. But our European users need invoices that show what they paid, and it's a manual process for us. I've been searching and I've found a couple options but none really scratch my itch.

On the flip side, I run a SaaS business (which I added to Paperboy), and we've often heard things like I didn't know I needed your service until I discovered it.

There are a lot of great tools out there and it's discovery and curation is not solved. Look at the success of Product Hunt, for example.