I have one of Philips, which I'm happy with. The light goes on half hour before the alarm is set to go off, and gets brighter and brighter (depends on the intensity you put it though, because I'm not such a heavy sleeper, so I don't need it to get to bright). If I don't wake up by that, a bird sound comes on.

The only down side is, that when I'm lying towards the lamp in the morning (mostly I'l lying the other way around though), I wake up pretty fast from when the lamp jumps on. But hey, I'm a light sleeper, so I don't think you will have that problem.