I try to read as little as possible about FO3 so it'll feel like a completely unknown game once I try it but it's hard not to get spoiled even when skimming through some threads.
From what I understand, it's more or less confirmed that you've been put to a cryo sleep for 200 years, as a part of a Vault-Tec experiment. I don't know what are the proofs but I've read about it on Beth, I think that even Pete Hines said something about it via Twitter.
One thing that really annoys me about the coming Fallout is the voiced protagonist.

If there's something I hate, it's to play with a forced voice. When a mod that disables voice actor, gets released, I'll be the first to download it.