It took three days after launch but it happened! And today (after another three days) I got my second one :)
It's only $19 per year each, but together with all the positive responses I got from the launch, it's more than enough motivation to keep working and developing my ideas for the project.
Some quick stats about the launch:
I published it on ProductHunt, HackerNews, DesignerNews, Reddit, here, and also sent an email to around 110 people who had subscribed on the pre-launch landing page. Most of the traffic came from ProductHunt, where it reached the top 10 of the day.
I got around 700 visitors on launch day, 400 the second, and so on, for a total of 1700 for the first week after launch. From those, up until today, around 220 people signed to try it. And of those, as mentioned, 2 people became paid customers :)
I have a lot more of work to do now.