I saw Up yesterday. It was, like all Pixar movies*, fantastic. It had a real sweetness, said something about life, had some laughs, cool action set pieces and looked gorgeous.
I saw it in 3D. While I still feel like the latest round of 3D-mania is just as much of a gimmick as it was in the '50's and '80s, if all the 3D movies use it so subtly like Up did, I would be more tolerant of the gimmick. In Up, they just used the 3D to really bring out depths. There weren't any, "Oh my god, it's coming right at us!" moments that I can remember.
I saw a trailer (in 3D!) for Zach Galifianakis's G-Force before the movie, too.
*I have yet to see Finding Nemo and I'm very apathetic towards seeing Cars