I think genius hour is a very useful time to do stuff that you like.  It lets you explore things that you want to do but are unable to do due to every day work. The time is limited so you concentrate on your work. This hour is the most productive hour. Most of the genius things like Gmail, Google Docs were a result of this genius hour which came out to be extremely popular. Genius hour in all is a great hour where people can come up with great ideas and discover great things.