I think you have a great and colorful app with neat design, the stats that you are providing are sufficient enough but they could be more interesting. I specially like the stats you providing about best sleeping night. I think if you could extend these kind of information to "best night of week", "best Monday's sleep", etc... this will all so much value to your app. Combining this with Badges will make it even more great. It also encourages your users to use the app more often.
PS: In my opinion, Nike+ Fuel has done a great job implementing this feature. Simple, Colorful and Informative.
Or instead of badges, they could be trophies? Just an idea..