We got the WALL-E DVDs on Tuesday and watched it that night. After loving the first act, I was disappointed by everything that happened on the ship after that. The appearance of the humans as a colony of fat blobs was distracting: "Oh, great, now for 60 minutes of fat jokes."
I watched some of the extras last night, and found out that the original story called for the starliner to be populated by fat alien gelatinous green blobs! (A little like the driving instructor in Lifted.) Pixar changed the story and character design on the fly, after 18 months of work, and the final appearance of the humans is a clear and reasonable evolution from awful green fat alien blobs to awful human blobs to soft, cuddly, sympathetic human blobs. In that context, the appearance of the humans is a little more sensible.
Since Erik wants to watch it once a day, it's growing on me. The first act is still way better than the rest, though.