As much as her continual appearance in the films began to get on my nerves I did think that Arwen was quite well done. The other Elves I found a bit bland (such as Arwen's guard person) or over the top (Elrond, Galadriel). The general appearance of the Elves was done well, they were tall and Cate Blanchett especially was very ethereal looking. I was very disappointed in the portrayal of Elrond to whom PJ did a great disservice. Elrond is supposed to be high and wise and dignified and they turn him into a jealous caricature.
The Hobbits were not as I had imagined them in the books at all. I had always had this vision of giant hamsters that walked on two legs - well not exactly but that's the best I can desribe them
Sam I think I saw as being reasonably close to my imagination as he was nicely plump and Pippin at least had the personality perfect. Frodo I must say I was never keen on so with that the portrayal was very accurate!