Finally got this and watched it this past weekend. The extra 50 minutes are a real addition to the movie. They flesh otu things that were only partially developed in the theatrical release, and add some missing scenes that I had been looking forward to.
The movie's one glaring flaw, to me, was the way two weeks of activity in Minas Tirith was condensed into the few minutes (or hours) that it took Frodo and Sam to get down a hill as they enter Mordor. That was a jagged break in the continuity of the story, to me. To my surprise, the addition of one scene - where Aragorn shows himself to Sauron in the seeing stone - fixed the problem. It explained why in a matter of hours, all the orcs in Mordor began moving towards the Black Gate. Admittedly, the transition shouldn't have been as abrupt as it was, but it's conceivable that it could have happened that quickly.
Overall, an outstanding addition to the LOTR ouevre. I'm into the second DVD of extra snow, and enjoying them immensely.