Hell, I don't even mind what they did with Faramir taking Frodo to Osgiliath. Because it gave him an arc, it gave him weakness, it showed the power of the Ring, and it gave Frodo something to do other than wander through the woods.
And I wish they did some of the changes they reneged on;
I would have loved to have seen Arwen directly contribute to the story and join the battle at Helm's Deep
I would have loved to have seen Sauron take physical form and fight Aragorn at the end.