Our daughter (3 years) loves her moon and sun. And since we got the Good Nite Lite we haven't had any problems with early wake ups! We didn't actually train her to wake up with the sun or anything, she's just sleeping past 6:30, which is all we ask. It may just be coincidence, but we sure aren't going to chance it by testing the theory! ;)
The thing that earns this night-light the coveted 5th star though, is that it not only ships with a battery, which is definitely not a given with kids products, but it ships with *TWO* batteries. The company packaged an extra battery in case there was something wrong with the first one! Now that is an extra touch of customer service genius in my opinion.