Well, it's definitely an adaption, and a better film for it; even if it will leave the canon-perfectionists foaming.
On the other hand, it would be nice if they hadn't moved the Whomping Willow since the last film, and made Hagrid's Hut bigger (and out of different materials), and indeed apparently landscaped the entire area around the castle :-).
They got the timing on the Harry-Sirius-Dementors-later!Harry sequence different the two times we see it, also (the first time around Harry falls over after later!Harry's wand turns off, the second time around it's before).
It's also rather irritating that they didn't take a couple of minutes to explain "Moony, Wormtail, Padfoot and Prongs".
On the other hand, the Knight Bus, Buckbeak and the Time-Turner were all wonderfully done. The geek in me spent a good couple of seconds trying to decide which bit of London the Cauldron is in (the slam-door trains suggest southern-London, and my guess would be somewhere between London Bridge and Fenchurch Street, but other suggestions are welcome), and which set of preserved coach-stock they used for the Hogwart's Express.
Remus didn't look like I imagine him, but worked really well, Sirius was quite correct, and I liked Peter's characterisation. slytherincesss will be irritated at how little screentime Pansy (Genevieve Gaunt) gets (she still reminds me of someone, I wish I could figure out who).
Oh, and the Marauders' Map was amazing!