The movies (and games) that the Blender Foundation sponsors serve two purposes.
First, they act as a showcase for the technologies currently available.
Secondly, and far more important for the software, the work flow and features required by modern animation teams drives the development of the Blender on. Sintel is built with the latest generation of Blender - 2.5 - which is still in beta. The requirements of Sintel have been developed in Blender in tandem.
Someone said 'it looks like a game trailer'. While I suspect it was intended as a put-down, it is actually a tremendous compliment. Modern computer games pack huge artistic and development muscle, cost tens of millions of dollars to develop and pull in the technical muscle of huge companies. That Blender can enable a small team of deveopers, animators and digital artists to produce something like shows the capabilities of the team and the software.