Excerpts from a spoiler-laden interview with Peter Mayhew, reprising his role of Chewbacca in Episode III:
"Lucas has really changed his writing style from back when he wrote the original trilogy. He is much bolder and willing to push the envelope in both settings and dialogue. In fact, the opening action scene involving many Wookiees takes place on one of the many new planets seen in this movie."
I guess having Wookies speak crappy dialogue is better than humans speaking crappy dialogue. Especially if they're CGI Wookies.