Gollum still holds up exceptionally well. Rohan sucks, wrong sort of land altogether. The Huorns are pretty poor and some of the model effects at the seige of Isengard are a bit ropey, and when they talk to Saruman all the actors are looking at the wrong place because when they did their bit the script said Saruman was on the balcony above the door (as in the book), but PJ put him on the roof as an excuse for more exciting cg shots- even though the distance between them is so great they couldn't have heard one another. Oh and as mentioned the Dead Marshes look awful.
But apart from that yeah TT looks fine.