Ahead of the launch next week, I've shared a link to the project to a small local developer group on Facebook to test the waters. Got around 15 likes (higher than average group activity - it's a very small group), a few shares, about 10 test projects created and a newsletter signup! And, crucially, no errors :-)
Last checks done, I'll probably launch on HN and tech-specific subreddits next week and see how it goes from there.