I finally went to the cinema to see Up yesterday and I loved it. The 3D effects were pretty good too, especially the times when they were flying. It was also surprisingly sad in places, something I wasn't expecting, as well as funny.
One of the things I love about these animated films these days is the attention to detail, they think of everything and will painstakingly animate individual items, no matter how many are involved. Like animating more than 10,000 balloons to lift the house! Whilst they didn't hand-animate all the balloons, they had to come up with a computer programme that could cope with that many individual balloons, and how they interact with each other. Quite a task in itself.
If you haven't seen Up already, I highly recommend it. Get down to the cinema, put your 3D specks on and enjoy!