FWIW, if I was starting a web app, I would focus on polishing the product based on the feedback of the users I have, to try and maximize conversion/retention ra

FWIW, if I was starting a web app, I would focus on polishing the product based on the feedback of the users I have, to try and maximize conversion/retention rather than exposure. In my first round of customers I'd look for feedback. I'd make more of a personal introduction; for example, post (with my real name and full disclosure) in some forums that have the demographics I want. Customers you get from press releases are less likely to bother and tell you what made them discard you. When the time comes to scale up, I would still spend as much of my time improving/polishing the app (p.s.: and the overall experience around it) as I have feedback to act upon. Word of mouth will make you or kill you.