Well, maybe I insist on too much accuracy but...
I felt the scene where the Borg ship lands in the Shire to assimilate the Hobbits was not true to the book. Also, Tolkien never implied that the Elves had photon torpedoes and had mastered subspace technology, so I found the scene where the elves warp in to save the fellowship of the ring and perform a classic 'Picard Maneuver' questionable at best. Gimli's constant use of the phrase 'I may be a dwarf, but I'm gonna cut ya Biatch!' seemed out of place to me.
Overall, I was disappointed with LOTR, although the lightsabre duel between Frodo and Saruman at the end, where we learn that Saruman is actually Frodo's father, was EXTREMELY well done.
Morgan Freeman did do an INCREDIBLE job playing the part of Gandolf!
Just my 2 cents...