You can't have a Sensor doing this job.

I love "The Lord of the Rings", I really do, and I've started watching the films one part at a time (as of last night).
They're actually very well done, and it was a huge undertaking and no one could have done it perfectly, but there are some things that I take serious issue with.
The acting and casting is great for the most part, except regarding Sam and Frodo. Last time I checked, Frodo wasn't a girl. Elijah Woods is one of the wimpiest, most effeminate actors they could have chosen. Frodo, in the book, was a bit wimpy once the power of the Ring grew stronger, but that had a lot to do with his age, not because he was a grade-A wimp. And Sean Astin is either yelling or crying in every scene.
A lot of stuff from the book was left out of the movie. Some of it wasn't exactly necessary for the plot to make sense (Tom Bombadil, Eowyn and Farimir, etc.), but when they cut out the Reckoning of the Shire, I started bawling my eyes out.
And if you're going to leave out stuff, you're not allowed to CHANGE or ADD stuff.
Several important examples:
Exhibit A: Theoden was NOT possessed by Saruman! He'd been lied to by Wormtongue and deluded into thinking the wrong thing, but he wasn't literally "possessed". Way to get this movie banned by Christian groups, Peter Jackson. Well, it probably wasn't banned by Christian groups (unlike Harry Potter), but you can bet Plugged In had a lot to say about it.
Exhibit B: I didn't mind this part so much, and "The Two Towers" didn't have a LOT of usable plot material, but the whole "Oh no, Aragorn is dead"? Thanks, Peter, it added tension, but you could have instead included the gigantic Warg fight on top of the mountain from the Fellowship instead. Because OF COURSE ARAGORN ISN'T GOING TO DIE IN THE SECOND MOVIE!
Exhibit C: I sort of understand this one better after reading a little bit about it, but they made Farimir out to be sort of a jerk, when he wasn't. And he shouldn't have taken them to Osgiliath. But, then again, Peter Jackson didn't really have much to do after deciding to save Shelob for the third movie. It just put sort of a negative light on Farimir, though he was redeemed and you could start feeling sorry for him again in the third movie.
Exhibit D: The moving death of Haldir. It confuses the little ones.

And that's about it. Surprisingly, "The Two Towers" might just be my favorite of the movies (not of the books, though). Liv Tyler kind of grosses me out, though - "The Fellowship of the Ring" is a close second.