The art style from the show has been greatly missed since the comics came out, and even more in this movie. If they do bring Zim back for another series, I hope they revert back to the original style.
Aside from the art, I enjoyed the movie and found it as entertaining as the show. I especially love the voice cast reprising their roles, and the humor of the show being represented in the film. Jhonen Vasquez is a brilliant writer with a hilarious view of his fellow man (one that I can't disagree with). I'm also immensely grateful that unlike the creators of "Rocko's Modern Life," they stuck to their story and didn't change any characters.