I just saw it, and it really hurts me to say how much I disliked it. Beyond the fact that anyone who hasn't read the books would be lost by the mix and match editing, and the offhand use of wizarding terms, it was just terrible.
It was just a mess of random things happening. As with Order of the Phoenix (only more salvageable because of some of the innuendo), everything was rushed together, and there was no mystery, no adventure, because they never spent more than a few minutes on any one thing. The bit at the end, with Snape revealing himself as the Half-Blood Prince just stank of the bit at the end of OotP, where Harry inexplicably claims that Voldermort will never know love.
There are so many problems with this film, it makes me angry that they're associated with the books I enjoy so much. Add that to the fact that this was the final book/film where the formula is retained; the whole "someone picks up Harry, he goes to Hogwarts, mysterious stuff happens, Harry gets suspicious, they figure it out in the end". Deathly Hallows is a whole other kettle of fish. They can't possibly fail to make it a bad movie; the parts they seem to fail at, are the narrative (like with Ron/Hermione or Harry/Ginny relationships).
Having said that, they even seem to ruin the biggest scenes. The cave, while a spectacle, lacked any weight for me, and it felt overdone. Then Dumbledore's big scene in the tower is ruined by Harry being able to stop Snape, but just not doing so. And by the major foreshadowing of Snape and Dumbledore discussing something at the tower -- another random event.
God.