ROFL, the sounds coming from my husband's seat when Aragorn went over the cliff and when the elves appeared was priceless. The elves was my husband's least favorite part. That honestly didn't bother me, because I had always hoped in the book that elves and especially dwarves would show up to kick some butt.
The portrayal of the Ents as idiots that had to be tricked into helping bugged me.
Gimli was used as comic relief a bit much. It was funny when he was up on the wall, but when he was tossed, well, yeah, that seemed hokey.
My husband felt like the elves coming was completely ludicrous and pointless to the plot, especially since they came from Rivendell isntead of Lorien. There should have been more than 300 men there, but since there weren't the elves did serve a purpose in the film, in my opinion. But the fact that there were so few people in Theoden's kingdom, what was the point of that? The women and children, instead of being sent to Dunharrow were sent to Helm's Deep. They were facing 10,000 Orc with only 300 men, but that just drew attention to how the full grown women were sending their young sons and doddering old dads out to fight while they were hiding. I know that Tolkien didn't have any women other than Eowyn fighting, and they weren't trained in combat, but this visual bugged me. At least in the book they weren't there, so it wasn't an issue. That didn't bother hubby at all, but then they only showed like 20 women and a few kids--Theoden was a king of a ragtag bunch. But I guess you can't make those films with 50 thousand extras anymore.

The secondary characters all just seemed spineless. Treebeard, Theoden, Faramir. Faramir was not supposed to be as weak as his brother, but that's exactly what happened. Plus, he wasn't as good looking at Boromir, doggone it!

Our friends like the movie, and liked the fact that Sam and Frodo ended up at Osgiliath because it was a way to introduce the men of Gondor in a different way, and have some different scenery. But they mostly seemed to be manhandling Hobbits and hiding from the Nazgul under their shields.
Shelob will be in the next movie, but I guess they decided to leave that part out and do it all in the third installment which isn't a bad idea, I don't think.
The part with Arwen was kind of boring to me, so I didn't really see the need of it. I assume that the reason that the whole attack with the Wargs was so that Aragorn could have this sort of dream sequence thing with Arwen. And I guess it made the movie more exciting, to those who aren't familiar with the book. I tried to keep an open mind about the plot stuff, but I really didn't like the way some of the characterization of the people was changed.
Then when Sam was saying "We don't belong here" my husband blurted out, "No, you don't!" ROFL