In a post on his official Facebook page, Peter Jackson answered a few questions about HFR 3D, aka high frame rate in 3D, aka 3D at 48 frames-per-second. Since 1927, all films have been shown at 24 frames per second, with The Hobbit: An Unexpected Journey being the first to show it at 48FPS in history. Because of the tech upgrade costs, it will be only shown on around 500 screens in North America (list here) so most will not be able to view it in the format that Jackson would prefer all see it in. Still if you in an area that will be showing The Hobbit in HFR 3D but on the fence about that extra 3D cost (the 48fps is a bonus), his Q&A may be useful in making a decision.

QUESTION: Why did you shoot The Hobbit Trilogy using the High Frame Rate (HFR) format?
PETER JACKSON: We live in a rapidly advancing digital age. Technology is being continually developed that can enhance and enrich the cinema-going experience. High Frame Rate shooting for a mainstream feature film has only become viable in the last year or two, and yet we live in an age of increasing home entertainment. I started shooting The Hobbit films in HFR because I wanted film audiences to experience just how remarkably immersive the theatrical cinema experience can be.
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Peter Jackson's Q&A on 48FPS. There are any Peter Jackson's Q&A on 48FPS in here.