Yeah, I didn't notice a speed problem either. They just seemed to be moving at a more natural speed-- which does look a bit weird compared to standard 24fps motion, I'll grant you.
The ironic thing is, I thought the strongest
moments in 48fps were during the flashbacks and slow-motion battles. The image was still super sharp and clear, but the slow-motion got rid of that overly-natural movement and gave the picture more of that magical LOTR feel.