Well, it takes some of the fantasy away. I no longer feel like I'm watching Gandalf walk around Middle Earth. I feel like I'm watching Ian McKellan walk around in a Gandalf costume. It's like somebody went to a LOTR play and filmed it with their HD phone.
That "movie magic" has always meant, to me, the ability to convey that what's happening on-screen could really happen - in whatever reality the film is set in. Advancing film to the point where it looks like we're watching a live stage presentation challenges that preconception I've always had. And raises the question: should there be a distinction - an illusion - associated with film? Without having seen 48fps, I can't say whether the challenge is justified. My only hope is that makes the suspension of disbelief easier so that I can just simply enjoy the story.