Regarding the Dursleys' treatment of Harry, that surprises me a little (again, every time): If they are worried he will hurt them, they should be nicer, shouldn't they? They shout at him for mentioning magic, for example. Then again, I suppose they are being as nice as they can (limited experience etc.), and they do get worse once they realise he cannot use magic. Hmmm.

Another, related, thing that struck me was that the Dursleys' preoccupation with keeping Harry from Hogwarts seems to suggest they actually care for him, in a warped, twisted way -- if not they would just leave him to magical life, surely? It would be less of a liability for them to have him at Hogwarts 10 months out of the year, than locked up in his room in their house (where he might suddenly lose control and start magicking the neighbours?

I also love how the twins have learnt how to open doors illegally the muggle way. They take their mischief seriously. That points forward to their later development, I suppose: their mischief is not an attempt to avoid hard work; it is often a product of it.

And I noted how Mrs Weasley told the twins to take a leaf out of Percy's book. I like how that sets up the later reversal, where the twins are heroes and Percy anything but. The later reversal would not be as effective if this wasn't there to lay the ground.