(nodding vigourously with all points. Yeah, on both sides.)
I love the movies, but there are some really really bad decisions in them. Which in a way may be the zen-type blemish that enhances the overall....if Spielberg had done them, there would be no jarring missteps, but there would be nothing new and breathtaking (also, the Nazi imagery would've been more than just the one scene).
IMHO, most of the missteps were in ROTK. The way Merry and Pippin joined up with Sam and Frodo sucked, as did the interesting physics of "Lean forward, Frodo! Your 80 pounds will affect this several thousand tons of falling stonework!" But otherwise, FOTR was amazingly good. I'm even reconciled to Arwen, although not to Liv.
TTT, I'm still wavering on Theoden's possession. The only things I really really hate from that movie are Slapstick!Gimli and the bullshit with the warg battle and disappearing Aragorn (tho they did give us Arwen the Magical Kissy Horse). The stuff in Osgiliath I hated at the time but am OK with now.
ROTK fell down hard for me, because every scene that was an emotional walloper in the book was changed for the movie, and lessened in the change. Pippin being tempted by the Palantir. Saruman's death scene (missing entirely, and even the one that will be in the EE isn't as meaningful). The Scouring, gone. The Fellowship's despair at the Morannon. Denethor's attempted destruction of himself and his son, his madness in general, and his death. It just comes off silly in the movie. Eowyn's descent into that dark desperate place, and her and Merry's victory over the Witch-King. Sam's choice.
The battles and the beacons were way more emotional than in the books, so I guess that's the trade-off.
watching FotR EE day before yesterday and during the scene at the end when he rescues him from drowning I got all sad thinking about Frodo making Sam leave in RotK
This is a great thing about these movies: the rewatch potential is amazing. I tear up at the Council of Elrond now when Mippin joins up, and I tear up seeing happy healthy Frodo.