If you are going to get Wall-E (and you should, oh yes you should) get the two disc edition... it's an odd wrapper, cardboard with bits that slide out, one per side each containing one disc.
I'm (unfortunately) prone to watching the extras before the main feature - and that's why you want the two discer because the extras on this one are good. Mind you, the two bonus shorts on the main disc - BURN-E and PRESTO! are both good too. BURN-E has a story about a poor maintenance robot that takes place in parallel with the main film...
PRESTO is a tale presented in the style of the classic Disney shorts of the 50's... superb CGI animated tale of a magician and his (hungry!) rabbit sidekick. You'll see what magic props are needed to do the old rabbit-out-of-a-hat routine and the dire consequences of their misuse....
There is a documentary that shows how Ben Burtt (sound craftsman on Star Wars as well) builds up the sonic landscape that adds verisimilitude to the main feature... how sounds can be sought, and simulated by amazing Heath Robinson-esque gadgets - something Disney's have done since the '30s, and we see some veteran pieces of kit dating back to before "The Reluctant Dragon", their use, and examples of sound-to-picture from classic Disney shorts.
All in all a superb little feature and worth seing.
The film itself? a heatwarming tale of robot love and self sacrifice, almost dialogue free but with a sonic landscape that is the aural equivalent of 3D. I enjoyed it a lot more than UP I can tell you.
Buy! Buy! Buy!