The Hobbit will be shown in several different ways, including 2D, 3D, IMAX and the new 48 frames per second. Most movies are shot in 24 frames per second. When there are as many as 48 frames per second, it stands to reason that it would look more realistic. Some people, however, think it actually just looks weird, and less realistic. There's too much detail and too clear, so it takes away from the film quality that people are so used to.
This website will tell you if a theater near you will be showing The Hobbit in 48 frames per second: