I'm almost at the point of launching my project -- in point 2, but I cut a lot -- and the things I'm most worried about are:

1. Once it's up and people actually use it, I have to be much more careful about uptime, monitoring, and changing how data is stored. This is by far the scariest thing.

2. Handling a large temporary spike in load when I publish the URL here or elsewhere

3. How -- if I actually knew what I wanted to charge for -- to integrate payment into the application, and what I'm supposed to do tax-wise with the money I'd get.