Summary

This game is not worth the suggested retail price and should be bought on sale or used. Not that it is not fun, but it lacks the kind of depth similarly-priced games like Legend of Zelda - Twilight Princess has. That game is worth every penny you paid, but the game-play in this one seems brief in comparison.

Strength

Beautiful and expansive terrain, with lots of items to find. Controls for casting spells is better than in previous HP games, and some of the boss battles can be challenging.

Weakness

The aiming reticule can be very frustrating, as are attempts to move items with magic. Like Metroid Prime: Corruption, this game's developer should have borrowed from Twilight Princess, which has an easy-to-see targeting reticule. Like Metroid, the targeting reticule can easily seem to disappear in the heat of battle.
Some of the mini battles (like with Slytherin enemies) are, because of a weak targeting system, almost impossibly random. Just stand a fire away, hoping you hit someone. DUMB!
But worst of all is the final boss battle with Voldemorte, which is beyond dumb and way too simple. In fact, it is downright silly; shake the Wii remote up and down, now left and right, until he is defeated. LAME, LAME, LAME!
Overall, I was disappointed, and wished I had found this at a yard sale for half the price.
My advice, wait for a yard sale!