Obviously it doesn't work until the third night of sleeping, because the first two nights are spent in calibration mode, so it's going to wake you up at the time you've set it too, no matter what state of sleep your in.
Mine has been going for a week now, i'll try get some data up later, i've felt quite tired still even when it's woken me up when it thought I should have been, the instance my eyes open I feel awake and then feel like I could fall back to sleep straight away.
Last night was the first time I used it yet it woke me up 15 minutes before the alarm, so I think your facts are incorrect.