I would go to the press as soon as you feel you're ready for public exposure (which you are, since you have around 100 users). That means now. Tell people about

I would go to the press as soon as you feel you're ready for public exposure (which you are, since you have around 100 users). That means now. Tell people about your service soon and often. I have a college textbook website that had membership triple from a press release to a local paper when I was just getting started. Don't be afraid to 'waste' your coverage now. Use it as soon as you get it. If you need more publicity, it's relatively easy to find another reason for the paper to cover you. My $0.02