Bought this after my 2.5 yr old was consistantly waking early. On night one we explained to her that she could only get up when light was green & sent her off to sleep as normal. When she woke early the next morning I took her back to her room, checked the clock & when it wasn't green convinced her to go back to bed. Every morning since (8 weeks now) she has successfully waited for the correct time, even sending herself back to sleep if particularly early.
Very much enjoy hearing her pattering accross the landing telling us it is 'wakey-wakey' time because 'it's green'! Also handy when you fancy a Sunday morning lie-in, nothing wrong with adding 30 mins or more to the alarm time :-)
Simple to setup and easy concept for a toddler to grasp - Green = go! Disagree with other comments re the nightlight being too bright, it gives off a dim light that is just enough to cast a glow into a medium-sized bedroom in my opinion.