The scene where the ents attacked Isengard, even though it was not in the book, was really cool. Stupid puny orcs got their asses kicked big time.
I don't really understand the signifigence of the Aragorn/Arwen love scenes, but they were VERY well done.
I thought that the Helm's deep battle was the best part of the entire movie. If they had made it any less spectacular, it would not have been enough.
And as for the Elves "not caring what happens to the Rohanians," OF COURSE THEY CARE!!!!! If it was the Elves being attacked, I would understand if the humans didn't come to help. The Elves, however, simply understood that what affected the humans would eventually affect them. They are supposed to be an ancient, wise culture, unaffected by greed and uncorrupted by power. Who cares if it was not in the book, I honestly would have been mad if they had not included that little bit. Also, like Ushgarak said, everyone loves the Elves.