It's fun.. until you've seen it all and spend hours walking back and forth.
But after a few hours doing that and finding some RoR members I became extremely bored. The endless walking to one end of Hogwarts and all the back to where you started just to complete a task is a real snooze. Not to mention that the combat battles get old and some tasks that you are required to do aren't explained too well and you are left hanging. The tasks will really get you VERY frustrated.
As for the graphics, the virtual recreation of Hogwarts is pretty amazing. But the characters do look the typical PS2 type quality.
The Harry Potter game series is a big letdown to the rest of the Harry Potter media. Overall, I'd stick to the book instead of playing this game.