I watched both the 24 and 48fps versions, and the 48fps version was MUCH better. A couple weeks later I watched Life of Pi in 3D and it was painful because of all the stuttering and lack of smoothness that the Hobbit had spoiled me on. Sadly, the only way I'll get close to it for now is to get the 3D Blu Ray of The Hobbit and turn on motion interpolation on my projector. It does an OK job, but I see frequent artifacts, which take me out of the experience. I'd much rather have a true 48fps version, or at the very least a way to pre-interpolate it with as much processing time as necessary in order to avoid artifacts around the edges of objects in scenes with fast motion and lots of objects. I wonder if there is a way to convert it to a h.264 version with pre-interpolated HFR.
Edit: I imagine there should be a way, since they've done it with the Hobbit and Avatar trailers, even at 60fps.