What hoped from investing in a working product would be, at least we had a little guaranty if the coins price is low, the project still have an actual product that can be used to back up the coins.
That little guarantee if turned into a big success can bring huge profits, lots of considerations when in terms of this investment inside ICO's, as there's a lots of duplicate project where competing with same target investors, it's all about how well you understand and how deep you research and learned about the project, working product is a plus attracting investors but the project itself should always be the first thing to look out.
Potentials can be learned if you are paying attentions with working products that has been offered while ico's are still ongoing.