I went to see it with a newbie (my mom), a semi-newbie (my dad-he loved them in high school, hasn't read them since), and my brother, who's started RotK, and was whining about the changes more than I was! I, fortunatly, didn't have to sit next to my mom, and thus didn't have to answer her questions.
I did sit next to my brother, who whined about the disappearance of Halbarad, Elladan & Elrohir, & Irmahil&Co. the entire time (kinda cute when he doesn't even like the books). Anyway, my mom did ask my dad questions, which (I believe) he was able to answer, either from whatever's left of his knowledge of the books (if you don't use it, you lose it, and he hasn't used it for about 20 years...), or from paying attention to the movie. My mom did enjoy it. She had watched the other movies a few weeks before. It was really nice to go with my whole family. It was like a family Christmas present. But now that it's in the budget theaters, I'd like to go again, alone, so that I can rethink it.