Just received this today and it's now being tested out by my junior gamester. Initial reaction, is that it's really captured the style and content of the films, with some great sound tracks, effects and dialogue. The game play looks up to the very best standard set by HP Yr5-7, and although its still early days it really does look to be very good.
Update: Two weeks in and it's still proving to be great fun, with so many characters, including 3 DLC packs there appears to be 91 possible (personal favourites are the Uruk-Hai and the Witch King), multiple mini-quests (a little like Assassins Creed), treasure/weapons to collect and areas to explore via a map. I'm assured it only took about ~6 hours play to run through the core of the game before free play was unlocked (which then allows many of the challenges to be tackled), at that point it looked like the game was about 15% completed (from recollection).
As others have said the sound track and dialogue are directly copied from the 3 films, which gives the game a depth and quality not normally heard from Lego games, certainly some of the screams/squarks are really quite realistic.