The extended version adds a few scenes that add some nice touches to the movie but are not in themselves that memorable.
However I think the real value of this extended edition is all the appendices that make up the story of the making of the movie.
There is a lot of content that has been edited very well into episodes about races, places and green screen spaces. The crew are the stars in these episodes and watching them go about their creative work, meeting crazy deadlines while having a lot of laughs was more fun to watch than the actual movie itself.
Highlights include the sound department trying to finish the movie on the very last day pulling an all nighter as they struggle to match Peter's vision, and when they nail it, its a perfect reality TV moment. Listening to Mikael Persbrandt the actor who plays Beorn is just magic, watching how he had to act with green screen tennis balls and his thoughts on doing so was hilarious. Lake Town breakfast and egg throwing scenes are hard to forget, the breakfast I'd like to forget but just can't.
Overall this boxed set is very good value – am looking forward to the next one.