I saw 48hz, but not the 24. In general I'd say my feelings were similar to yours, but without the other version to back it up. It definitely made the whole movie feel like a unique experience, and highlighted the character acting significantly (for better or worse). Overall, glad I saw it at the high frame rate, and given the opportunity I will likely do so with the future installments.

Also, if I know my lore right, I think it does make sense for Gandalf or any of the other wizards to refer to it as Middle Earth, whereas none of the other characters would. Possibly one of the really high elves like Galadriel, since she had been to the west-lands before as well.