Wow. While the Fellowship of the Ring and the Two Towers left me feeling that they couldn't have been better translated to this medium, they didn't offer the opportunity Return of the King gave Peter Jackson in the finale of the epic. Verdict: Don't miss!
I really feel sorry for the Return of the King crew for achieving so much in this film that I feel they should've achieved more.
If it had been an entirely methodical transliteration from the literary medium, only the small Tolkien quasi-fanatic part of me would've been satisfied, but it wouldn't be as good a movie as the Jackson interpretation. But having seen what Jackson did, the stout fan (but not fanatic) of Tolkien in me felt he could've done more interpretation (away from straight transliteration) to make it more accessible to those who aren't multi-time readers of the series. So in doing so well in the film, he overcame the sacrosanct nature of the source work in my belief, allowing me to be critical of him. What a nightmare!
I was asked earlier about my feelings about the movie, and here is some of what I discussed:
Overall, most of my (high!) expectations were met, and a few were exceeded - amazing considering the fan-fueled hype surrounding the movie. In some cases, these were the same expectation, like in the Shelob case. Sorry, I have to have spoilers.
Shelob didn't seem nearly as malignly intelligent as I understood her to be from the Two Towers and other supporting material from Tolkien. She wasn't quite as scary as I imagine she could've been in her lair itself - I think the lighting was wrong there. I do recall Elijah Wood looking suitably scared, however. Outside, it's another story. It's absolutely magic on screen, especially when she's not expected to leave the lair. Possibly the best visual scene in the movie occurs here.
Leading up to Shelob, the stairs weren't quite what I'd imagined from the source material. I remember it being a small climb per step, with horizontal bits in-between, not the long climb it appeared to be. Overall, a reasonable change, but I'm not sure what the desired effect of the change was.
Gollum behaved pretty much unchanged in the film. I'm not sure I liked the opening episode regarding Deagol's finding of the ring and Smeagol's capture thereof. I imagined the ring's call at that stage to be less obvious, and the faces of the actors and their fight didn't sit well with me.
I'm not so happy with the dead Aragorn enlists - their appearance is at not corporeal enough, almost comical, appearing animated in a film that otherwise looks realistic. I also feel the Osgiliath episode could've just ended as the dead army appears, leaving us with a picture of the Orcs looking afraid. Next we see them, they're arriving at the battle for Minas Tirith. Seeing them perform twice is a bit boring. They're just way too powerful too, I suppose that's because the Mordor army is overwhelmingly powerful.
I really had high hopes for the large-scale battles, but I felt let down there. Again, large numbers of cavalry somehow mostly avoided the Orc hordes with their prepared polearms.
However, once in the fray itself, it's quite beautiful. The unprepared Orcs further in are trodden underfoot by the charging horses. That said, all the Mordor army seemed to die way too easily.
Legolas and Gimli don't have much to do in the source material for the third movie, so they've been put to use again as comic relief (now that Merry and Pippin are being occasionally serious). While I enjoyed the competitiveness of the elf and dwarf, I feel something could have been found for them to do. That said, Legolas taking down the Oliphant was suitably impressive and elegant, and Gimli's retort priceless.
The Eowyn/Theoden/Merry/Witch-King of Angmar episode was very well done, doing more than justice to the book. Mostly; Eowyn and Merry don't suffer from the Nazgul's black breath. The Healing Halls is probably Extended Edition material, though.
The Gollum/Frodo/Ring episode just doesn't sit right for me, but I'm pretty sure this is because of my interpretation of the book's account of it. I'm a bit worried about the emotions in this episode - Frodo isn't as compelling as I imagine he could've been. It's not that Elijah Wood was incapable of doing it, but he didn't seem to do justice when claiming the ring: not doing the dark and broody and rising-evil and lack of self-control believably. Also, his reasons for attacking Gollum at the end - is it to get rid of the ring, or to reclaim it? I think that was a missed opportunity to see Frodo realise the folly in claiming it. That would combine better with what, to me, seemed like a quick recovery from the lack of the ring to escape the crumbling volcano.
Gandalf was a lot less of a supporting character in this film than he was in the predecessors; he was slightly depowered in the Fellowship (at Elrond's Council and at the entrance to Moria). But Ian McKellen's performance (as any excellent performance) makes one feel that nobody else could have played that part. He's not what I felt Gandalf was like from my reading of the book; he was a whole lot more. More human, more wise, more at peace and comfortable with his tasks as an Istari and his rebirth as Gandalf the White. This allows him to have a sense of humour, which McKellen displays to good effect. Finally, he's not been translated as a High-Magic fantasy wizard, but rather a wise old man with good intentions and a few subtle powers. The encounter between the Witch-King and Gandalf is another thing I hope to see on the Extended Edition.
The one major decision of Peter Jackson's that I question is not doing the Scouring of the Shire, even for the Extended Edition. I feel that it brings closure to the Saruman story arc left hanging in the film edition of Return of the King, and claimed to be changed to happening at Orthanc in the Extended Edition. But besides this, it tempers the victory and the high expectations the hobbits have had of returning home. I felt it was a big message in the book; Tolkien's swipe at the glorification of war. It probably didn't belong in the film edition anyway; the film is not diminshed by its absence (save the closure of the Saruman arc), but Tolkien fans are going to be unhappy.
As I said, my verdict is that you should not miss this film. Don't even think about not watching it. It's enough reason in itself to overcome any reluctance to watch the first two, whether you're a Tolkien fan or not.