I am a huge Harry Potter fan. Read all the books, seen all the movies, played all the games. That said.
This was by far the worst HP game ever. (all the other ones were good just not this one)
In a nutshell the graphics, music and voice acting are all beautifuly done. Amazing even. What sucks about this game is that you spend all of your time cleaning up the castle or else searching for useless stuff. There is no health meter so Harry never has to really fight or worry about being in any danger. There are no big bosses to battle or even little bosses. You spend the majority of your time rehanging portraits, straightening up lopsided suits of armor or fixing broked statues. Essentially, Harry is a janitor. Or if you prefer, custodial engineer. Either way it is a waste of time.

Having played each of the various video games based upon the first four Harry Potter films & books, it has been interesting to observe how each new game has evolved beyond the differences in each of the stories that each game is based. For example, the third game ("Harry Potter and the Prisoner of Azkaban") was the first to permit a player to play as a character other than Harry: in addition to Harry, the player could also play as Ron or Hermione and switch between any of these three characters at will at any point during the game. The third game was also the first game in which successfully finding collector cards had an overall impact upon game play. The fourth game ("Harry Potter and the Goblet of Fire") again allowed the player to play as Harry, Ron or Hermione, but unlike the previous game, the player had to remain as the chosen character for the duration of a particular level. Also, collector cards had a much greater impact upon the game as they defined what abilities or stamina the particular player would have based upon which three cards the player chose to use at a particular time. While the first three games had players wandering about Hogwarts (and sometimes other locations), the fourth game was more restrictive in that a player could not just wander anywhere.

What, then distinguishes the fifth game ("Harry Potter and the Order of the Phoenix") from its predecessors? First, it is the first Harry Potter game available for next-gen video consoles. Second, more than any previous game, the rendition of Hogwarts Castle is the most accurate to any of the films and permits a player to go anywhere within its walls. Third, no beans or collector cards: but not to worry: there are plenty of other types of achievements that impact game play. Fourth, programmers went out of there way to ensure that game achievements are very closely related to the film: so (for example) no battling of monsters that are unrelated to the film and/or book, and no unusual tasks for obtaining spells. In the fifth game, spells are learned as needed. Finally, the player cannot choose which character to play as. Though this sounds as though fifth game programmers went backwards, quite the contrary is true: for the first time, a player can play as characters that have never been permitted before: as Dumbledore, Sirius, or even as one of the Weasley twins; albeit, at precise moments during game play to match similar moments in the film and/or book.

As a very task-oriented game, a player will find himself (among other things) seeking out the Room of Requirement, finding secret passages, putting together & training "Dumbledore's Army", coping with Delores Umbridge, carrying out "OWL" tests for specific professors, battling students, playing a myriad of games (chess, gobstones and card games) against other students and cleaning up Hogwarts. Yes, in the fifth Harry Potter video game, you will find yourself making beds, sweeping, mopping, repairing broken objects and turning on lamps & heaters. Why, you may ask? Simple: to earn points & achievements. As you complete various tasks, you not only earn points and achievements, you increase Harry's magical powers. You also get to unlock hidden rewards that include interviews with actors who participated in the film & game, as well as other information about the fifth film. The rewards are made available to you in the "Room of Rewards" and you will be visited by Moaning Myrtle each time you earn another reward. You'll learn something about occlumency from Professor Snape and you might get to help create a bit of havoc around the castle to upset a certain woman in pink.

With superb graphics, fun & engaging tasks, a ton of interaction with lots of characters around Hogwarts (including the paintings), and more, the "Harry Potter and the Order of the Phoenix" video game is sure to please any Harry Potter/video game enthusiast. My overall rating for the game is 5 out of 5 stars and I highly recommend it.