In some ways, I feel like they're screwing the story (And the Animated Short): The Modern Whoville was dark and dirty, and probably an unsafe place to represent how Humans destroy forests and cause the heck they live in themselves. The fact that it's sterile instead of dirty in this movie makes me feel like a sad Panda (or maybe a very angry Lorax).
But in other ways, I feel like their tapping into something ingenious! Think about it: The reason why the Once-ler doesn't look like the Once-ler in the past is because at first, he was doing what he did for good intentions: He looks young, naive, and fool hearted, which is exactly how most people are before they enter politics or Business management. As he grows old and as the his world around him turns dark, he will turn into a Grinch-like thing from his own mistakes, and his own arrogance. If they do that in the story form, then they have already won me over.
I'm leaning to go see it even if that's not the case, what with the Awesome voice actors (Danny DiVeto mostly). I hope they do it in the Story form, I really really do.