On the whole, I really enjoyed CoS. I wasn't expecting it to be as good as it was, actually. It stuck quite faithfully to the book for the most part, and where it didn't, the changes mostly made sense. Except that outpouring of Hagrid-love at the end, which I agree was just plain weird. I would also have liked to see more shock and upset from Hagrid at the prospect of being sent to Azkaban. The way he acted made it seem as though it wasn't that big a deal.
There was also more Snape in the movie than I'd been led to believe. And all his scenes were terrific, especially the bit where he's taking Harry and Ron to task for flying the car to Hogwarts (just watch the way his hands prowl across the table as he gets up from his seat to berate them -- it's a wonderful bit of physical acting) and the Duelling Club scene, where he and Kenneth Branagh are clearly having way too much fun spitting bits of scenery at each other. Snape's fitted frock coat in that scene also puts paid to the complaints some fans made after PS/SS that Rickman was "too fat" for the role. I'm glad to see that the costume and makeup people seem to finally be getting the hang of Snape.
Jason Isaacs' portrayal of Lucius Malfoy was, as many have already observed, terrific -- though mercifully he kept the character devoid of any redeeming personal qualities, so I don't feel at all tempted to write Lucius fic. Tom Felton was better as Draco this time around too, although "better" in this case means "just as much of an insufferable brat as he is in the book", so I won't be writing Draco fic any time soon either.
I can see how both H/Hers and R/Hers would get a big kick out of this film. Lots of little touches (literally) between Harry and Hermione, although I feel obligated to mention that when kids of that age "like" each other in the romantic sense, they are far too awkward and self-conscious to do that kind of thing. So Harry's holding Petrified!Hermione's hand and talking about how much they need her actually argues rather strongly that Harry doesn't think of her as more than a friend. In the last Great Hall scene, however, when Hermione moved as though to hug Ron, and then hung back looking embarrassed and shook hands with him instead, Chris Columbus might as well have taken out a big fat red marker and written "R/H" across the screen. Hold your horses, Chris, they're only twelve!
(Mutters to self: Twelve. Remember that. Harry is twelve. Even grubby and carrying a sword. Twelve.)