Its been a while since I've used the mac app-store since my recent switch to pc. I have found that the app store is cluttered by apps that are simply useless and either preform poorly or not at all. If the app works well I would say that the next step is adding mini purchases within the app. This could be things like language packs, mathematical equation inputs, ect. I would go to people of different majors and see what kind of things they most often wish they could transfer from their notebook to their laptop. That will give you the best idea of what to add next.