Look at the comments for the reviewer that gave it a rotten rating:
WALL-E - Movie Reviews, Trailers, Pictures - Rotten Tomatoes
Seems he "accidentally" deleted his review (and all the negative comments associated), so he had to post it again. People took this really well...
I'm sure Wall-E will be great. I don't know if they'll ever be able to top Incredibles though. I like most Pixar movies in a different type of way than normal movies (as in I really like them, but they'll never be Jurassic Park, Matrix, Star Wars, Godfather, etc), but Incredibles rose above that and actually was good for both the reasons I like Pixar movies, and just as a movie in general.
To date, I've enjoyed all of the Pixar movies, except Cars, which was sort of boring. Ratatoullie (sp?) I think put them back on track, and I think Wall-E will keep them running.
Also, Pixar =
