Just got back from seeing it in HFR.
This was basically me nearly the entire way through:
It did the things I expected it to: it brought a new level of clarity and detail to the picture, it helped to make the great CG look even better (Gollum, Azog, and the eagles were glorious to behold), but also served to make the dodgier moments that much more noticeable (especially the lesser green-screen backgrounds, like Radagast escaping the orcs and the meeting of the Council), it made the big, fast pans that Jackson is so fond of look absolutely sublime (with special mentions to the entire Goblin Town sequence, holy shit), and it certainly made how each scene was lit that much more important, as the gathering of the dwarves in Bilbo's home looked barely different in motion, outside of the flames, while anytime it was outdoors or on a wider soundstage, the increase in framerate was immediately obvious. I don't know if it's the right decision for every kind of film out there, but I do know that I will absolutely be seeing any future film that is available in HFR in that format.
That being said, my brother wasn't nearly as taken with it, as he holds the common complaint about the actors looking sped up, and the way I explained it to him why I didn't feel the same way was doing a comparison between a console version and a PC version of the same game, which he seemed to understand right away. He still prefers 24fps, but he definitely made note of many of the same improvements that I just described.