About thirty pages into second book. Quick thoughts on first book:
1) Why do the rest of the Hogwarts teachers and students put up with Slytherin? It's obvious they suck. They're really the only thing besides He-Who-Must-Not-Be-Named stopping Hogwarts from being perfect.
2) The Dursley's are a little too constantly dickish for my tastes. I guess it does get you firmly on Harry Potter's side though. One problem I struggle with in my own writing is always wanting to portray both the negatives and positives of every character, to the point that you don't really have anyone to "root" for.
3) Good plot twist with the Snape-Quirrell thing. I wonder if it's as effective in the movie? I just googled Quirrell and he looks way more obviously evil than in the book. Either way, i thought it was a good move since it complicated Snape's character and made the ending more surprising. I'm not sure that all the details added up in retrospect, which is generally my problem with plot twists. I'd have to look back over some of the scenes with Snape and Quirrell earlier in the book.
4) I guess the Slytherins are not all bad. Snape did save Harry's life. But he was still a huge dick about it. I guarantee you one of the Hufflepuffs would have been nicer about it.