I didn't see it in 3D, so I can't tell you about that. It was still a wonderful hour and a half. The first ten minutes of the film shows little Carl Fredrickson (the grumpy old man) as a child. Then within minutes you are emotionally connected to him and his wife as it plays through their life without talking--only well orchestrated music. After that montage, I knew that this would be a great movie.
The rest of the movie is filled with adventure, a lot of humor, odd characters, and an evil villain. I, and those around me, laughed a lot. After seeing the previews, I was afraid that Russell, the little kid, would get tiresome shortly into the movie. But he didn't. I'm not quite sure where this fits in my list of best Pixar movies. I'll have to wait and let it sink in.
One of the reasons Pixar succeeds is they are willing to take risks. There were several times during the movie that there was complete silence on screen and in the audience--as Carl flips through the Adventure book his wife had made and thinks about her, for example. And just the idea of doing a story with an old man as the main character was thought absurd by many because it's not marketable. But, Pixar doesn't follow conventional wisdom. And I am so glad they don't.