I think it is more about paradox instead of fear. a)you want to add enough features to attract/impress potential users. b)you want to ship it, so you can get f

I think it is more about paradox instead of fear. a)you want to add enough features to attract/impress potential users. b)you want to ship it, so you can get feedback asap. a) and b) are pulling to opposite directions, hence the paradox. There is no easy solution for this. However, if you change the question to "what do I need to build to test my assumptions (about the market and user)", the answer will be more obvious.