Yikes! My wife is the one who uses it, and hasn't had any problems so far except that it does run down it's battery pretty quickly. You pretty much need to charge it every day.
She has trouble sleeping in general, and usually wakes up before the time set, so it's hard to say. What she likes about it is the data about how restless she was, and that lets her correlate it with other things going on during the day before and after.