I think they should've included more information on who this Half-Blood Prince is. Because at the end of the film when Snape said, "ZOMG I am the Half-Blood Prince mwahahahahahaha," it didn't seem as impacting as it should have.
Also the end of the film seemed kind of like it abruptly stopped. So far, each Harry Potter movie has some kind of "epic" ending except Half Blood Prince:
Philosopher's Stone/Sorcerer's Stone: Harry confronts Professor Quirell, who's hiding Voldemort
Chamber of Secrets: Harry fights the basilisk and destroys a Horcrux
Prisoner of Azkaban: Harry yells "EXPECTO PATRONAAAAAAAAAAAAAAAAUUUUUUUUUMMMMMMM!!!!!!!!!!!!!!!!!!!!!!!!!"
Goblet of Fire: Harry has some epic fight with Voldemort
Order of the Phoenix: Dumbledore and Voldemort have an epic duel
Half-Blood Prince: Snape says, "ZOMG I'm the Half-Blood Prince mwahahahaha fear me lolololololol"
Then again bear in mind guys that this film was the longest book yet so considering that I think they did well. The last 2 films will (hopefully) be freakin' awesome.
Order of the Phoenix is a longer book than Half-Blood Prince. Ironically, Order of the Phoenix is the longest book and the shortest movie. In fact, the Half-Blood Prince book is shorter than Order of the Phoenix AND Goblet of Fire.
Oh, and the Bonham Carter person that plays Bellatrix Lestrange is awesome. Altough her character in the film seems different than the book (less aggresive), she makes Lestrange look like some crazy psycho lady, which is how I imagined it when I read the books.