Harmy,

If you watch the Hobbit trailer, you can see what it looks like at 24 frames per second. There's no "Saving Private Ryan" choppiness. It looks just as it would had it been shot at 24 fps. Remember, they need this to look good on what will still be many 35mm projectors. That's the whole reason they're shooting at 48 and not 60, they still need to make 24-frame-per-second versions for 35mm, blu-ray, etc.

The Avatar sequels, meanwhile, might take even longer to reach the screen. Cameron and 20th Century Fox had originally said 2014/15, but Cameron's producer Jon Landau recently said "four years from now," which would put it in the 2015/2016 time frame. By that point, there may very well be enough digital projectors deployed in movie theaters that eliminating 35mm prints from the equation might not be a big problem and Cameron can just shoot at 60fps.