Same here. Sure it had plenty of battery life left last night. Tried to power up this afternoon and got nothing, just a cold black screen. Put it on charge for a good four or five hours and still nothing. Can't even reset it via the power/volume combination.
Waiting to hear back from Samsung, but unless someone can suggest a cure I guess it will have to be shipped off to be serviced. Shame, because it's a great little tablet.