Hi,
I've used one for a few years (I'm on my second) mine is a Phillips alarm type one, it was a gift (purchased from John Lewis I think)
I'm not morning person and suffer with the dark mornings and evenings. I think it does help with waking up in the morning, as the light gradually comes on before the alarm goes off and I have the alarm noise as bird song which gradually gets louder. I find I'm not woken up with a start.
Happy to answer any other questions.