In a nutshell, Wall-E is a sci-fi, robotic love story and it's amazing. Since most of the story revolves around two barely-lingual robots, there is almost no dialogue. The story is told almost completely through image and sound effects. I'm assuming that the team at Pixar knew they would need to bring their A-game to make this work and it really shows. You really fall in love with these characters. It's amazing how much emotion Pixar can make you feel towards a trash-collecting robot or a fish or a toy. I think that's what makes them so great. Even though they make the most visually stunning animated films out there, they get that it's ultimately not about the technology, it's about the story. And they tell stories like few other film makers.
Even though I loved Kung Fu Panda and it's nominated in the same category as Wall-E, this award should go to Wall-E hands-down. It's a stunning movie, a moving story, and well worth your time.