However, of the 20 or so people that have said they definitely want to use it only a couple have actually become active users.
I'm trying to get a sense of how long it takes after launch to get active users - people that actually use it regularly.
I also had a private beta before launch and the beta users converted across.
I don't think this question is really going to help you though, as it varies for everyone and is not an indicator of how well you're going to do. You're probably best wondering/asking how do you get more customers. That's what is relevant now. Not how you compare to other unrelated businesses in different industries.
PS : People are by nature appreciative of one's work. So they are going to say - i love your product, get third/fourth degree people to use it and get their feedback from your friend (hopefully you would get a correct feedback)
Sounds close to http://en.wikipedia.org/wiki/Pareto_principle thus far.