The film cells are quite cool.
Fellowship I think is my favorite movie because it centers the viewer in the world so much. I thought there was too much fighting proportionally in TT theatrical, but the extended was perfect with all the world-building and character development back in. Some scenes didn't even make sense without the extended cut (Brego picking up Aragorn).
I'm hoping that's what happens with RotK. I'm hoping the extended version doesn't add a single frame of fighting and adds more talking. I'm spoiled after Fellowship's almost documentary approach to Tolkein's world that the battles can drag a little. I'm glad I saw the whole trilogy consecutively, because otherwise I might have gotten a little tired of the fighting in RotK.
However, that's the way the books are. My only complaint is the Sam rescues Frodo from the orc tower scene. It bothered me when I watched it that they took out Sam wearing the ring; I think that makes the scene what it is, that once he's tasted the power of the ring same can still give it up. However, upon reflection I realized that they could not have had Sam put on the ring based on how quickly Sauron has seen the ring every other time its been worn in the films.
So then my only question became... why leave Frodo's capture in at all? The scene did not serve any real purpose except for the brief scare with Sam holding the ring, which could have been done any number of other ways. Also, the whole tower of orcs wiping itself out was rather trite. This didn't hurt my enjoyment of the movie for more than a few brief seconds, but I hope the extended does something to give more of a purpose to this scene.
Also, because I like the near-documentary approach, RotK was harder to swallow because it was more ambitious. It was more high-fantasy than the low-fantasy of most of Fellowship (excepting the Sauron and Balrog scenes). That meant that what was on screen wasn't going to look real no matter what; however, they did an amazing job of making it look authentic. As a result of the weirdness of it, though, there were times when I didn't feel as fully immersed in the world as I was in the previous two films.
Overall, though, here's how I would rate them:
Fellowhip: 10/10
Two Towers: 9/10, 10/10 extended
RoTK: 9/10 in context, but had I seen just it it would have been more 7 or 8/10. Jackson tends to cut what I consider good stuff, so the extended will undoubtedly increase that number.
The reason the scores are so high is because of near-flawless writing and acting (I can only think of one line I don't like in any film- Theoden's "so it begins"), the realness of the world (no plastic looking sets or crappy CGI and the distinctiveness of the cultures), and the fun, cinematic (if ocassionally a bit long) action scenes (you couldn't have done Tolkein with realistic battles, especially not with Gimli and Legolas's contest).
Furthermore, excepting the Sam rescuing Frodo quibble, I universally loved the changes from the book. Tom Bombadil had no place in a movie; his character is simply too ethereal to have fit with the straight-forward approach of Jackson. The change to Faramir and the elves showing up at Helm's Deep showed on screen what the reader had always had to imagine symbolically or psychologically; we got to see, physically, the temptation of Faramir and the passing of the world to Men from the elves (think the scene when Haldir died). The army of the dead attacking at Minas Tirith rather than capturing the mercenaries avoided complicating the battle or having to do a flashback to another battle right after the big one.
All in all, I think they'll go down in many people's hearts, if not the critic's lists, as the best movies ever made (including in mine). It's going to be difficult for the film to receive spots in any "best of" lists because there are 3 of them that are so seamlessly woven together, because of the "movie" fight scenes, because of their popularity (alot of critics only like things that are "elite"), because of their straightforwardness, and because their fantasy. Well, those people suck.
Can't wait for Jackson's Hobbit...