We have the DVDs but I was thinking about getting these blurays for DH since they are cheap right now and we have a new TV and blu ray player. Is it worth the $?
Yes, get the extended editions. There was lots of good stuff left out, b/c a 3-hour movie taxes not only bladders but also the movie theater's ability to get in enough screenings in a day.
The added/expanded scenes are clearly identified in case you're interested, but I recommend just sitting back and enjoying. Get the Blu-ray Extended if you can afford it or have found a good deal, by all means. These movies really show off a hi-def player.