The Half-Blood Prince Quick Look and the demo of Order of the Phoenix I found on Live Marketplace both seem to be all kinds of terrible. In terms of gameplay they look bland, and fail to capitalize on the fun that might be had being a powerfull wizard in Harry Potter's universe. First off, for gameplay, a rail flier and a potions mixer are two of the worst ideas ever. There must be ways to make it fun, perhaps you have to guide the ingrediants from one side of the bowl to the other, Viva Pinata Style, and after they touch the bowl churns a bit and more ingrediants are poured in quick. That might be no fun as well, but it'd be gameplay.
Second all the usage of characters in the games are terrible, the acting poor, and the appearances a bit off (Slughorn not fat enough this time around, should be walrus size). Honestly, if they want to be a good game (they don't, though they might after all the movies pass), they would choose a location that involves a lot less of Hermione, Ron, Harry, Dumbledore, the whole lot, and focuses on characterizing the world, and the details of the magic. They could do a game where you're an Auror in the Original War, kicking ass and taking names. They could spend a game in an American School in the Harry Potter world where they don't care about Quiditch at all, and infact call it Ruffletop and call a FPS like sport Quiditch. They could put you in the shoes of Harry as an Auror if they really want it to be about Harry, so long as the action is solid.
Also a thing about the dueling club from the end of the quick look, Stupefy should knock a bitch out. Like in one hit. Sure, it's kinda crap for gameplay, but then you could just change HP into stamina, and make autoblocks take it out of him.