It is rather enlightening how many things you can find wrong with your application when doing user testing. Here are a couple of things that people were concerned about:
1. User wanted to challenge other people to goals broader than quitting something. They basically wanted to the goal or challenge part to be way more open-ended.
2. The virtual points system was meaningless, thus there was less of an incentive to “see through a challenge”. Virtual prizes maybe? Someone suggested actual money, but someone else said that actual money might deter people.
3. They usually wouldn’t “dare” or challenge people to do anything constructive or productive. It would just be a silly daring game to see who can do the stupidest or most non-productive stuff — which is exactly what we planned against.
4. User didn’t like being the only one doing something, wanted more of a group aspect
5. Likes the idea of a hall of fame/shame to keep users accountable and as an incentive to complete challenges. Hall of shame is an especially powerful incentive, negative reinforcement.
We would take these into account when implementing our final design iteration — well, some of them.