Spoilers TTT Towers Over Its Predecessor - Film is a worthy complement to the book
In short, it has. Yes, it's darker overall -- but so is the book. Yes, Faramir's character was less noble than in the book, but in this case, I thought it did achieve the purpose of driving the plot forward, where the over-emphasis of Saruman in the first movie did not. And yes, Treebeard was a bit too menacing and brooding for my taste, and seemed to do little besides carry the hobbits through the forest; but that was, for me, the only significant weakness in the film, and probably could not have been resolved without another 15 minutes of exposition.
As for the highlights, well, pretty much everything else matched or exceeded my expectations. Topping the list was the marvelous depiction of Gollum and his relationship with Frodo and Sam. I always did like that part of the story better than the battle tableaux at Helm's Deep and Minas Tirith, and this movie scored a bull's eye. Interpreting Gollum's trademark utterance, "gollum, gollum" as a sort of hacking cough was a brilliant touch. Moreover, the Dead Marshes scene was nowhere near as horrific as I'd been led to expect, and Gollum's rescue of Frodo from the water demons (or whatever they were) established his character (Gollum's, that is!) as sympathetic.
A close second favorite would have to be the battle scenes, including the encounter with the warg riders. Jackson's representation of wargs as hypertrophied hyenas rather than outsized wolves was interesting. The buildup to Helm's Deep, with shots of marching berserker orcs was also impressive.
Then there was Gandalf's opening sequence with the Balrog - it worked perfectly, although I left regretting not being shown the balrog as a "thing of slime, stronger than a strangling snake," not to mention the "nameless things" that gnaw the earth that Gandalf encountered.
Merry and Pippin's adventures with the Uruk-hai were scary, but again, not overdone and certainly in keeping with the spirit of the book.
Finally, I loved Rohan, although the exorcism of Saruman was a little odd. However, I always found the Theoden/Wormtongue sequence to be one of the weakest in the books, since Tolkien spends only a page or two establishing the malignant influence of Wormtongue - and then has him tossed out. Theoden's transformation always seemed too sudden, and Wormtongue's departure too abrupt, to be convincing. PJ's version, however, actually outdid the books (I know, heresy, but Tolkien, for all his genius, could no more write a perfect book of this scope than PJ can create a perfect movie); Dourif's Grima is a marvelous villain, and a fine (if brief) foil for the resurrected Gandalf.
Oh, and by the way, I liked the Arwen sequences and thought they were an appropriate romantic counterpoise to Eowyn's developing love for Aragorn. Tolkien's critics have half a point when they claim Tolkein had no strong female characters, and point to Arwen as evidence; she really serves no obvious purpose at all in the novels. Of course, those same critics conveniently overlook Eowyn, whom Miranda Otto really did justice to. I can hardly wait to see her clash with the Witch King!
Overall, the best thing about this movie was its length. PJ and co. were unafraid to lay out the whole story - knowing that this time around, they have a sure thing. If only they'd done the same with the first movie! The pacing and mood were very even, unlike FOTR, which oscillates between Stygian darkness and languid sentimentality.
In sum, this is a movie that Tolkien fans can embrace with very few reservations. It's very apparent that PJ learned from many of the mistakes of FOTR. I plan to see this one many times. It's one of the greatest movies ever made, especially of this length. Nothing can ever take the place of the books, of course, but this movie is a worthy complement.