I enjoyed this short film quite a bit, though of all the films nominated for Best Animated Short this year, I think it and "Let's Pollute" have the least chance of winning the Oscar. We'll see--the winner is to be announced next week.
The film is odd because it's is a story within a story. It begins with a mother squirrel (Helena Bonham Carter...who, incidentally, doesn't seem that squirrelly to me) almost being caught by a bird of prey. She scrambles into her nest and tells her children a story about a mouse and when he was captured by predators--and how the clever mouse escapes.
The film is extremely cute and enjoyable. However, the character animation seemed only fair--and compared to many other CGI films of the last few years it does not compare well. This does not detract horribly from enjoying the film and the film's backgrounds are quite nice. All in all, I have no other negatives about it other than the character design and I am sure young kids will love it.
UPDATE: I was surprised, but just moments ago I saw that "The Lost Thing" won the Oscar for Best Animated Short. To me, this was a surprise!