Maxwell is ok for rendering frames, but I doubt that it would ever be used for movies, especially by Pixar. It took them 50 hours per frame to completely render out the movie "Cars" in MR, so Maxwell is probably out of the question for movies.
But then Maxwell doesn't need much tinkering with. Still, I like MR because of that IPR render. If you mess up in Maxwell, you'd waste a lot a time fixing problems and waiting to render over and over again.
"The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man."
George Bernard Shaw - Man and Superman