It was a very refreshing area/section the plot of Platinum. I loved the aesthetics of the world, and I particularly enjoyed the puzzles. (Which proved quite a challenge!) Compared to other areas that had puzzles, the Distrortion World would probably have to be the one that made me use my problem solving skills the most. It was great.
One thing I would have loved to have seen though, was (as like Narnia mentioned), wild Pokemon. It's true that not a lot of Pokemon would want to live in such surroundings, but that doesn't mean all of the wouldn't. What about ghost, dark and perhaps even psychic types, that thrive off shadows, darkness and everything warped and twisted?