I must be an anomaly then - I have a fairly regular sleep cycle despite the bright, LCD Monitor I use. What sometimes causes me to get to be a little later isn't the bright monitor, but what I might be doing at the time. Playing a game, or doing some creative writing will keep me awake far longer than me just browsing the internet.
I wonder if their study took that into account? You can't do much more on the Kindle other than read something, whereas an iPad, Laptop or even my old Palm T|X can do so much more. So did their test groups actually DO the exact same thing on their given devices?