I've been Pottered =) It's a good book... I don't understand why the first book is sometimes called "The Sorcerer's Stone" and sometimes "The Philosopher's Stone". "Philosopher" sounds better to me - it sounds more subdued and less flashy.
J. K. Rowling just "gets it" about children. From what I've read so far, the story is not a dumbed-down version of an adult story plotline. It's a sophistocated storyline but from a 11 year old's point of view (ie. the beginning of the Formal Operational stage of cognitive development).
The only other author I've gotten this feeling from is Beverly Cleary (all the books about Ramona Quimby, Henry Huggins and Ralph S. Mouse). And maybe Robert C. O'Brien (Mrs. Frisby and the Rats of NIMH).