I really like the fact that this whole challenge thing seems to be geared toward helping me and the other participants make improvements in our lives without constant commercial interruption. Also, the task-oriented challenges force me to do activities that I normally wouldn't do within a 24-hour period.
I liked the challenge "make a list of five major things you need to complete in the next week and write them down somewhere that you will see them on a regular basis." I've also started writing down cash payments and asking for receipts at places I go so I can file them in an envelope instead of throwing it away.
Some of the Daily Challenges have helped me bring awareness to other areas of my life, like work and health. Now, I often am more aware of making better choices.