My 2 cents: before a public launch, try to find discussion forums that suit your target demographic and try to recruit users for an alpha version, ask opinions and feedback. This way you can try to create an early adopter community before launch and at least get very direct feedback - much better way to start than shouting into ether.
I've been thinking through the same problem recently, and while I don't have any good suggestions myself, I did find the following particularly helpful, perhaps you will too:
First, thanks for higlighting the Balsamiq post and related HN discussion. A lot of good insights: http://news.ycombinator.com/item?id=267639
My 2 cents: before a public launch, try to find discussion forums that suit your target demographic and try to recruit users for an alpha version, ask opinions and feedback. This way you can try to create an early adopter community before launch and at least get very direct feedback - much better way to start than shouting into ether.