Are you going to see it?
(Tooth surgery first though, she's no mood right now to do anything.)
One problem with LOTR was the poor dramatization of the relationship of Aragorn and Arwen...we are left to the appendices to figure it out and to discern her characterization. When I read LOTR for the first time as a teen, I thought, "And Aragorn rejected Eowyn for this figure?". Took the appendix to explain it.
There's no way an audience that isn't immersed in Tolkein (like me) could accept Aragorn's eventual rejection of Eowyn with no sense of who Arwen is and the sacrifices she is making (losing her immortality, her Elfhood, and her family to the West)...I think PJ has a workable answer here. Movies have to be different from books, to show instead of tell.
I've been reading of other changes that bother me more than drawing Arwen as a more active character...like elimination of the Scouring of the Shire, Killing Saruman on some sort of wheel in TTT...
I can't wait to see the ents!