About a couple of weeks ago I made https://everydaycheck.com public. It's a minimalist habit tracker. It's ridiculously simple, you add some habits, and try to create beautiful chains by doing the tasks EVERY DAY. I have lots of ideas, of course, but the core idea is already there and it works.
I shared the link in a couple of reddit communities and one of the posts literally exploded ( https://www.reddit.com/r/getdisciplined/comments/60akoi/method_thought_i_owed_this_subreddit_a_lot_so_im/ ). It got me over 2.500 visits and over 800 signups. Of those, about 80-100 people come back every day to use the app. I think it's a very good ratio and it's helped me fix a lot of small issues and get feedback from the users. It has certainly validated the idea.
At this point, I have a dilemma. I believe the app is too simple to charge for it but at the same time I don't want to keep investing too much time on it if I cannot make any benefit from it. With the validated idea I kind of want to validate the 'business' itself.
I'm hesitant between:
Wait for a month to see how many users are still using it almost daily, while trying to grow the user base.
Start charging now. (how much/model to be decided)
Send an email to everyone on the database asking straight out, would you pay for this and how much?
Ideas on how/how much to charge are also welcome!