Regardless of whether it is an ad or not: You missed a huge chance by submitting to HN before having the app ready. I find the idea of only a few categories appealing, but if I wanted to do this right now I would probably go look for an app that is available right now. I want to test your app for a week or so, give feedback and move on if it doesn't work. Not too keen on signing up on a mailinglist for an app that will "someday" be ready, unless I'm very excited about it or the app is the first one to solve a specific problem. Attention spans are short!