Oh and for those of you who have finished book one:  did any of you figure out the "who-dun-it"?  I don't think we've talked as much about that aspect of it.  The book is a wonderful kid mystery.  Especially later on in the series, there are so many clues to try to pick up on.  I guess that goes along with the intricate plotline we've already talked about.  Anyway, I was surprised by the ending.  Since it was a children's book, I wasn't expecting twists in the story at that point.  
Yeah, I don't think I figured out the mystery in Book 1 either.  I'm not particularly good at who-dun-its anyway, but JKR always managed to keep me guessing throughout the series.  Even when I thought I had it figured out, I was never totally right... and usually I was just plain wrong LOL.  But that's what made it more fun, cause I could be shocked by all the twists!
I never had anything spoiled for me, thankfully.  I remember when the sixth book came out, I heard later about people who got the book at midnight, flipped to the end, and then rode around shouting out their car windows, "____________ kills ___________!!!" to everyone who was lined up at the bookstores for the midnight release parties.  I saw a video of one after the fact.  Isn't that horrible?!  People completely flipped out, they were so pissed off, which I can totally understand!  I avoided the internet and everything too until after I had finished.