If anyone has Sky HD there's a 90 min documentary about Pixar on Anytime at the moment - I presume it will be on one of the film channels at some point too.
It covers the demise of Disney 2D animation and the shift to 3D CG animation in great detail. Pixar are basically the new Disney with hit after hit (I don't think they've had a dud yet). Their key is not the method of animation, rather the people involved in making the films, how they come up with the stories etc... In the early days of 3D animation Disney shied away from it becuase it took too long and was too expensive. Precisely for these reasons Pixar had to make sure each and every film were as close to perfect as possible - they simpley couldn't afford to produce a bad film. Disney made a stack of money distributing the early Pixar films and as a result thought they could churn out 2D films in parallel and make money from them without making the bigger scale films like Alladin, Lion King etc... As it turned out by then Pixar had employed all the best animators so Disney's film were awful. Now Pixar are owned by Disney and are responsible for both 3D & 2D films, employing the same animation techniques for both types, so future Disney 2D films should be much, much better.
Watching this documentary was very interesting and reminded me how much I love both the traditional 2D and new 3D animations. So much so I'm going to see Wall-E later.